Four-term U.S. Rep. Lou Barletta, R-Pa., a staunch supporter of President Donald Trump who first got national notice as a small-city mayor for his attempted crackdown on illegal immigration, on Tuesday won the Republican nomination for U.S. Senate in Pennsylvania.

Barletta paid little attention to his Republican rival, state Rep. Jim Christiana, during the primary campaign. Instead, he focused his attacks on the candidate he hopes to unseat in the fall, two-term Democratic Sen. Bob Casey.

With 80 percent of precincts reporting, Barletta led Christiana by nearly 112,000 votes out of more than 495,000 cast. The four-term congressman will face an uphill battle against the two-term incumbent Casey and Fox News' current projections show the seat is likely to remain in Democratic hands.

"Lou has established himself as tireless advocate for Pennsylvania families," National Republican Senate Committee Executive Director Chris Hansen said in a statement, "and his strong record of success will undoubtedly lead him to victory over Bob Casey and his history of flip-flopping on the issues that matter to Pennsylvanians."

Casey, who was unopposed for the Democratic nomination, has opposed Trump's Supreme Court pick, many of his highest-profile nominees and the GOP tax-cutting law.

"Tonight, I'm going to appeal to those Democrats and independents in Pennsylvania who voted for Donald Trump," Barletta said in a victory speech to supporters. "If you are a Democrat or an independent who voted for Donald Trump, you cannot vote for Bob Casey, who is going to stop every single thing that you voted for and the agenda that this country is on and the progress that we're making in America today."

Casey is among 10 Democratic senators seeking re-election this year in states won by Trump, making him a target for Republicans.

"This election will be a choice between a candidate who fights for working families and a candidate who fights for the corporate interests that stack the deck against them," Casey's campaign said in a statement. "It will be a choice between a candidate who stands up to President Trump when he’s wrong and a candidate who believes President Trump can do no wrong."

Barletta's victory continues President Trump's winning streak in contested Republican primaries. Barletta was a Trump supporter before the 2016 presidential nomination was settled. That loyalty earned him Trump's early support in the Senate race, as well as recorded telephone calls last weekend featuring the president backing Barletta "fully, strongly and proudly."

Last week, Trump urged GOP Senate primary voters to support Rep. Jim Renacci in Ohio and oppose former coal company executive Don Blankenship in West Virginia. Renacci won and Blankenship lost.

In the GOP gubernatorial primary, state Sen. Scott Wagner was projected to narrowly defeat businessman, Army veteran and first-time candidatae Paul Mango and face Democratic Gov. Tom Wolf in November.

Wagner, a waste-hauling millionaire, pumped more than $10 million of his own cash into his campaign and has spread hundreds of thousands more around the state since last year to boost GOP committees and candidates. But he will be an underdog against Wolf, who holds a substantial money advantage: Wolf headed into May with $14 million in his campaign account, while Wagner reported $2.2 million.

While Republicans focused on primaries for statewide office, Democrats have been keeping a close eye on races they see as key in their efforts to win back the House of Representatives.

A whopping 84 candidates were running in the Keystone State’s 18 House districts Tuesday, more than in any election year since 1984 when the state had 23 seats in the House. Seven of those 18 seats are vacant, due in large part to the departures of five Republican lawmakers who either have resigned or are not running again.

The Pennsylvania Supreme Court added another wrinkle to the race in February, when it redrew the district boundaries in a way many observers considered favorable to Democrats. However, the overload of open seats has resulted in several oversized Democratic primary fields – such as in the new 7th District, where six Democrats were running to replace Republican Rep. Charlie Dent, who has stepped down. No fewer than ten Democrats were running in suburban Philadelphia's 5th District, where Rep. Patrick Meehan resigned last month amid allegations he sexually harassed a former employee. Both districts voted for Hillary Clinton over Donald Trump in the 2016 presidential election.

In the southwest corner of the state, the new 14th District offered a chance at redemption for state Rep. Rick Saccone. In March, Saccone narrowly lost a U.S. House special election to Democrat Conor Lamb in the old 18th District, which overwhelmingly voted for Trump in 2016.

On Monday, Saccone told Fox News that the 14th District was "a much stronger district for a person like me." Early projections on Tuesday showed Reschenthaler leading Saccone by a 55 to 45 percent margin during Tuesday night's primary, The Hill reported, citing 97 percent of precints.

Lamb, who is running in the new 17th District, has no Democratic primary opponent and will face off with Republican U.S. Rep Keith Rothfus, who currently represents the old 12th District, in November.

Elsewhere, Democratic voters in the new 1st District were deciding between millionaire trial lawyer Scott Wallace and Rachel Reddick, a former Navy officer. Wallace, who has spent heavily on the race, has fought allegations of carpetbagging over his move back to his home state from Maryland after he reportedly was recruited to run. Others have criticized Reddick for being a registered Republican until 2016.

"When I saw Democrats needed a candidate in Bucks County, I knew I had to step up," Reddick said in a recent online campaign ad. "I won't be afraid to stand up to Donald Trump."

The winner of the three-cornered fight between Wallace, Reddick and Steve Bacher will face Republican incumbent Brian Fitzpatrick in November.

Polling day was marked by stormy weather that knocked out power to a handful of polling stations near Scranton, delaying the counting of paper ballots, while a storm-related gas leak temporarily closed a polling place in the tiny borough of Delaware Water Gap, in the Poconos, according to the Pocono Record. Officials there kept it open until 10:30 p.m.

Fox News' Joseph Weber, Michelle Chavez and The Associated Press contributed to this report.