PRESENTING YOUR I-95 PRIMARY FIELD GUIDE
Whether you call them grinders, subs or hoagies, there’s a pretty decent chance that if you are Northeastern Republican, it’s primary day for you.

It’s a piece of the primary calendar that has had remarkably little scrutiny in recent years. The Republican calendar is designed to give moderates like John McCain or Mitt Romney a boost with blue states in the late going. Much like California on the last day of balloting, these primaries are scheduled to provide stopping power against insurgents.

Or not…

We’ve talked before about Donald Trump as Bizzaro World Romney: a Northeastern, socially moderate businessman distrusted by the party’s conservative base. Trump has what Romney lacked: a passionate core group of followers. But he is only just now gaining what Romney had: the support of the party’s elite and the backing of its professional class.

But, ready or not, here he comes. Trump will perhaps not do as well overall in Maryland, Delaware, Pennsylvania, Connecticut and Rhode Island as Romney did four years ago, but he is almost certain to win.

How much Trump wins by, though, is quite material.

On the Democratic side, it doesn’t really matter. Whether presumptive nominee Hillary Clinton wins by 2 points or 20 points, it’s all about the narrative. Bernie Sanders can’t really catch her. And while she could win so big today that her race was not just substantially over but actually done, it’s only a question of time. She will not be denied.

Trump, however, needs both the narrative and the delegates. So we’ll leave the Democrats to their own devices today and focus on the hunt for the 172 delegates on the GOP side.

The stakes are these: Trump needs clearly to win all five contests, even if by pluralities, for the sake of momentum and claim at least 100 delegates for the sake of math. If Trump moves another furlong ahead of Sen. Ted Cruz today, Cruz’s task in must-win Indiana next week becomes that much harder.

With that in mind, let’s meet the last folks in America who still know what a passenger train looks like.

[Watch Fox: Megyn Kelly and Bret Baier bring you the latest as the first results roll in at 6 p.m. ET]

PENNSYLVANIA
For today’s primary contests, Pennsylvania is the one that matters the most. It has the most delegates on the line and the weirdest allocation system.

Only 17 of the state’s 71 delegates are given to the state’s overall primary winner. The remaining 54 are directly elected within their congressional districts – three for each of the 18 districts – but are unaffiliated with any campaign on the ballot.

This means that voters will elect delegates that aren’t officially supporting any particular candidate and are not bound to any candidate ahead of the national convention in Cleveland.

In normal years, that makes them objects of affection and desire among campaigns. This year, they had better just hope they have unlisted phone numbers. This will also require campaigns to continue to have a strong ground game in Pennsylvania beyond today’s vote, something that Cruz has been far more adept at than Trump throughout the cycle.

Even though Trump enjoys a 20-point lead over Cruz in the Real Clear Politics polling average in Pennsylvania, his delegate gains are likely to be substantially smaller.

The keys to the Keystone State are, not surprisingly, in and around Philadelphia and Pittsburgh. But there are some gains to be made in the broad expanse in between the home turf of the Stillers and the Iggles.

--71 total delegates
--17 at-large, 54 congressional delegates
--Winner-take-all statewide, unbound delegates elected on the district level.
--Closed primary
--811,706 total ballots cast in 2012
--Mitt Romney, 58 percent; Rick Santorum, 18 percent; Ron Paul, 13 percent; Newt Gingrich, 10 percent
--Polls close at 8 p.m. ET

Bucks County: Frilly Philly
--Population: 626,685
--Median household income: $76,824
--Race: Caucasian, 89 percent; black, 4 percent
--Adults with bachelor’s degrees: 37 percent
--2012 election: Obama 50 percent
--Residents 65 or older: 17 percent
--Yardley is where George Washington and his men set off for their history-turning Christmas Eve raid on Hessian troops dozing across the river in Trenton.

Washington County: Pittsburbs
--Population: 208,187
--Median household income: $55,323
--Race: Caucasian, 94 percent; black, 3 percent
--Adults with bachelor’s degrees: 26 percent
--2012 election: Romney 56 percent
--Residents 65 or older: 19 percent
--Site of the Whiskey Rebellion in 1791, when Scots-Irish residents rebelled against a tax on their currency: distilled spirits. President Washington, ahem, disagreed with their interpretation.

Centre County: They are Penn State
--Population: 160,580
--Median household income: $50,295
--Race: Caucasian, 89 percent; black, 4 percent
--Adults with bachelor’s degrees: 40 percent
--2012 election: Obama 49 percent
--Residents 65 or older: 12 percent
--Pennsylvania Match Company was founded in 1899 and was among the leading producers of wooden matches in America until World War II.

MARYLAND
Like Pennsylvania, Maryland is divided into three states: the rural western Panhandle, the D.C. suburbs and the shore. But unlike the Keystone State, Maryland awards all of its 38 delegates today.

The panhandle and the areas around Baltimore County are pretty much a slam-dunk for Trump, but the D.C. suburbs of Montgomery County will prove challenging for the Republican frontrunner. This area is similar to Fairfax and Loudon Counties in Virginia, which went heavily for Sen. Marco Rubio in their primary back in March. Gov. John Kasich can expect to see some support kick in today.

Further out in Frederick County is where Cruz will see his votes aiming for the sweet spot between the more liberal conservatives in Washington area and the fervent Trump supporters in the outskirts. These areas are more conservative by nature, yet are still affluent areas that are not natural to Trump’s base.

--38 total delegates
--14 at-large, 24 district delegates
--Winner-take-all
--Closed primary
--248,468 total ballots cast in 2012
--Mitt Romney, 49 percent; Rick Santorum, 28 percent; Newt Gingrich, 11 percent, Ron Paul, 10 percent
--Polls close at 8 p.m. ET

Montgomery County: Club Fed
--Population: 1,030,447
--Median household income: $98,704
--Race: Caucasian, 62 percent; black, 19 percent
--Adults with bachelor’s degrees: 57 percent
--2012 election: Obama 71 percent
--Residents 65 or older: 14 percent
--Among the 10 richest counties in America.

Frederick County: Out West
--Population: 243,322
--Median household income: $84,480
--Race: Caucasian, 83 percent; black, 9 percent
--Adults with bachelor’s degrees: 39 percent
--2012 election: Romney 50 percent
--Residents 65 or older: 13 percent
--In 1862, Confederate Gen. Robert E. Lee seized Frederick’s train yards in order to choke off supplies to the Army of the Potomac, but failed to arouse what he hoped would be an uprising of support for the rebellion.

Baltimore County: Down to The Wire
--Population: 831,128
--Median household income: $66,940
--Race: Caucasian, 64 percent; black, 28 percent
--Adults with bachelor’s degrees: 36 percent
--2012 election: Obama 57 percent
--Residents 65 or older: 16 percent
--Bengies drive-in theater in Middle River is the largest continually operated movie theater screen in America.

CONNECTICUT
If Trump delivers in Connecticut the way he did in his neighboring home state of New York, the Constitution State’s unique allocation of delegates won’t be a problem.

But...

Connecticut awards their 10 statewide delegates to the winner with over 50 percent, which based on neighboring New York’s results could be a possibility for Trump. If no candidate reaches that 50 percent mark then each candidate with 20 percent support receives delegates proportionally based on their results.

This would still be good for Trump because even if he doesn’t clinch a 50 percent mark, he’ll likely be very close to it meaning he can still walk away with a majority of delegates.

The district level delegates are awarded to the winner of each of the five congressional districts. Areas like Fairfield County just outside of the greater New York City area is where Kasich may find his support. These are the affluent, well-educated types of voters that gave him a congressional district in Manhattan last Tuesday, so there’s a chance he could snag a few delegates here.

The rest of the state looks a lot more like Hartford County with its blue-collar roots, post-industry boomtown with the same ethnic populations of the Trump strongholds we’ve seen in New Hampshire, Massachusetts and New York.

And if the state’s Republicans were once willing to pick a pro wrestling executive as a Senate candidate in 2010, why not one of its characters for president?

--28 total delegates
--13 at-large, 15 district delegates
--Winner-take-most
--Closed primary
--59,578 total ballots cast in 2012
--Mitt Romney, 67 percent; Ron Paul, 13 percent; Newt Gingrich, 10 percent; Rick Santorum, 7 percent
--Polls close at 8 p.m. ET

Fairfield County: Ahoy, polloi
--Population: 948,053
--Median household income: $83,163
--Race: Caucasian, 80 percent; black, 12 percent
--Adults with bachelor’s degrees: 45 percent
--2012 election: Obama 55 percent
--Residents 65 or older: 14 percent
--As with all counties in Connecticut, there is no county government or county seat. Each town is responsible for all local government activities.

Hartford County: Remember the Whalers
--Population: 897,985
--Median household income: $65,499
--Race: Caucasian, 77 percent; black, 15 percent
--Adults with bachelor’s degrees: 36 percent
--2012 election: Obama 62 percent
--Residents 65 or older: 16 percent
--The Hartford Courant is recognized as the oldest continuously run newspaper in the United States, beginning in 1764.

RHODE ISLAND
Meet the Buddy Cianci Republicans.

The former Providence mayor, who died in January, had some disagreements with the federal government. But he might have credibly run for mayor in 2014 despite his criminal convictions if it weren’t for the cancer that killed him. A colorful crook who favored tough tactics, locals loved their hard-knocks mayor.

A wide authoritarian streak runs through Rhode Island’s Republicans, much like those in New York. So it’s no surprise that Trump should ride roughshod everywhere from Federal Hill to Warwick.

The rules for delegates, though, are as slippery as a quahog.

The Ocean State also awards their statewide delegates proportionally with a mandatory 10 percent threshold. In the congressional districts, if one candidate receives 67 percent of the vote then that candidate receives two delegates and the next highest candidate receives one. If no one reaches 67 percent then the top three candidates with a 10 percent threshold each receive one delegate.

These rules somewhat favor Trump who is expected to sweep Rhode Island in today’s contest. Even those in highly affluent areas like coastal Washington County are unlikely to have enough Kasich voters to give delegates to anyone but the Republican frontrunner. And most of the vote share lies in Providence County, a highly ethnic, working-class town that looks a lot like Boston and Staten Island making it an expected sweeping victory for Trump in the state’s most populous county.

--19 total delegates
--13 at-large, 6 district delegates
--Proportional
--Open to Republicans, unaffiliated voters
--14,564 total ballots cast in 2012
--Mitt Romney, 63 percent; Ron Paul, 24 percent; Newt Gingrich, 6 percent; Rick Santorum, 6 percent
--Polls close at 8 p.m. ET

Washington County: Chip off the old Block
--Population: 126,517
--Median household income: $72,784
--Race: Caucasian, 94 percent; black, 1 percent
--Adults with bachelor’s degrees: 44 percent
--2012 election: Obama 57 percent
--Residents 65 or older: 18 percent
--Known as “South County” it has some of the best seaside spots in the eastern states, including Block Island and Watch Hill.

DELAWARE
With only one congressional district, Delaware looks to be a sweep for Trump across the board. The rules here are pretty simple: majority wins it all. This makes things even easier for Trump. The main stash of voters is in New Castle County where the capital, Dover is, but those in the beach communities in Sussex County will likely be just as strong for the Republican frontrunner.

--16 total delegates
--13 at-large, 3 district delegates
--Winner-take-all
--Closed primary
--28,592 total ballots cast in 2012
--Mitt Romney, 56 percent; Newt Gingrich, 27 percent; Ron Paul, 11 percent; Rick Santorum, 6 percent
--Polls close at 8 p.m. ET

Sussex County: Under the boardwalk
--Population: 210,849
--Median household income: $53,505
--Race: Caucasian, 83 percent; black, 13 percent
--Adults with bachelor’s degrees: 22 percent
--2012 election: Obama 57 percent
--Residents 65 or older: 24 percent
--Every two years, the community of Georgetown has a festival known as Return Day, two days after Election Day. The holiday originates from colonial times when the town would gather to hear election results and end any animosities with a traditional ox roast.

[GOP delegate count: Trump 845; Cruz 559; Kasich 148 (1,237 needed to win)]

Chris Stirewalt is digital politics editor for Fox News. Sally Persons contributed to this report. Want FOX News First in your inbox every day? Sign up here.

Chris Stirewalt joined Fox News Channel (FNC) in July of 2010 and serves as digital politics editor based in Washington, D.C.  Additionally, he authors the daily "Fox News First" political news note and hosts "Power Play," a feature video series, on FoxNews.com. Stirewalt makes frequent appearances on the network, including "The Kelly File," "Special Report with Bret Baier," and "Fox News Sunday with Chris Wallace."  He also provides expert political analysis for Fox News coverage of state, congressional and presidential elections.