Updated

The Democrats last, best chance to hold the House this fall won't come from a last-ditch infusion of cash in key races. It won't come from some special electoral gimmick. Nor will it materialize in the vaunted tradition of unveiling an "October surprise," a last-minute revelation concocted to drown Republicans in a damning political scandal.

No. The Democrats final hope lies in marine sedimentology.

You heard right.

It's really quite simple.

After their big electoral gains in 2006 and 2008, Democrats knew that a Republican wave was forming just off the political surf reef break. They knew this wave would race in, its curls of water spilling over themselves as it approached the shore. But Democrats had questions. How do they handle this wave?

If it's just a usual political "pipeline" wave that hits the president's party in midterm elections, then they'd grab their boogie boards and ride it out, Hawaii Five-O style. The wave would crash into the shore and take with it 25 to 30 Democratic House seats. That was something tame and manageable.

But what if the wave swells, whipping the shore with 39 to 40 Republican seats, just enough to award the GOP a bare majority? Or is this wave something special? Is it a tsunami along the lines of the 54-seat catastrophe that washed up on the Congressional shore in 1994? Or could it be something unprecedented? Is it the "big one," a wave capable of lashing the Capitol with a storm surge so massive that it submerges the Dome with 60 or 70 GOP seats?

No matter the size, there's only one way to break a wave. And that's with rocks and cliffs and strata. Which Democrats have been erecting for two years. The question now is have the Democrats built a sufficient seawall? Or is this wave so staggering that no breakwater can protect the Democratic coastline?

The Democratic bulkheads against the GOP tide come in two forms: 1) House Democrats holding contested seats in swing districts amid the worst electoral conditions in years and 2) Democrats surgically plucking off a handful of Republican seats to offset Democratic losses. In other words, addition by subtraction.

During a Christian Science Monitor breakfast last week, Democratic Congressional Campaign Committee Chairman (DCCC) Chris Van Hollen (D-MD) told reporters that he warned vulnerable Democrats to gird for battle this year. Most listened and at least have a fighting chance.

But...

"There are a few members who we approached many, many, many months ago to get their act together who did not take that advice," Van Hollen conceded.

So the question is whether the Democratic seawall is strong enough.

For instance, Republicans put several veteran House Democratic committee chairmen in their sights long ago: Armed Services Committee Chairman Ike Skelton (D-MO), Budget Committee Chairman John Spratt (D-SC) and Natural Resources Committee Chairman Nick Rahall (D-WV). Messrs. Skelton, Spratt and Rahall are all moderate Democrats who represent districts with GOP leanings. But they all got Van Hollen's message early and solidified their sea levies by raising cash and campaigning hard.

"They're our rocks against the tide," said one senior House Democratic aide of the trio.

But there are other races where Democrats are optimistic that junior lawmakers can serve as a bulwark against the Republican sea.

Republican Congressional hopeful Tim Burns told me in May that the special election in southwestern Pennsylvania to succeed the late-Rep. Jack Murtha (D-PA) was a "bellwether" of things to come this fall.

Two hours later, Burns conceded to Rep. Mark Critz (D-PA), a longtime Murtha aide.

In the spring, it was thought that Murtha's southwest Pennsylvania district was ripe for a Republican pickup. The steel and mining economy is stagnant, jobs are scarce and many worry about the "big spending" agenda in Washington. Murtha's old seat remains in play this fall. But now Critz boasts the "power of incumbency," which ironically may actually help him in a decidedly anti-incumbent year.

Other junior lawmakers that buckled down include freshmen Reps. John Adler (D-NJ), Gerry Connolly (D-VA) and Michael McMahon (D-NY). Each flipped a Republican seat to a Democratic seat. All might not win re-election. But they gathered sandbags and mortar to help build Van Hollen's dike.

Another good example is freshman Rep. Alan Grayson (D-FL). In 2008, Grayson seized another seat that had long been GOP turf when he edged out former-Rep. Ric Keller (R-FL). No fool he, Grayson amassed a substantial war chest in an effort to ward off any serious Republican contender. As of October 13, Grayson had raised more than $4.8 million and had $814,000 on hand. His opponent, Republican nominee Daniel Webster only cobbled together $1.2 million and had less than half the cash reserves as Grayson.

Still, the race is a tossup. And if Grayson ekes out another win, it shows you just how expensive the Democratic floodwall was to keep that particular seat.

In the past few weeks, other races popped up on the radar that no one thought would be in play. Rep. Charlie Wilson (D-OH) is locked in a dogfight with Republican challenger Bill Johnson. Wilson didn't take his race for granted. But most political handicappers believed Wilson would be fine this cycle and focused instead on five other Ohio Democrats from swing districts.

Across the Iron Range of Minnesota and stretching to the Canadian border, you'll find House Transportation Committee Chairman Jim Oberstar (D-MN) fighting for his seat against Republican upstart Chip Cravaack. Two weeks ago, Minnesota's Star-Tribune ran a piece titled "Has Oberstar Met His Match?" No Republican has held this Congressional district in northern Minnesota since just after World War II. But Republicans are enthused about Cravaack's surge, especially after former House Speaker Newt Gingrich (R-GA) predicted it to be "one of the great upset stories in the country this year." Oberstar is running more TV commercials than he's had to in years.

Oberstar may win. But the fact that some prognosticators believe his seat is even on the board shows the electoral torrent that's churning on November 2.

But one only needs to travel south to truly understand the type of work Democrats have to do this fall to brace against the coming storm.

The 7th Congressional District of Arizona is about as different as one can get from Jim Oberstar's. The district runs from the Phoenix suburbs all the way to California and to the Mexican border. Rep. Raul Grijalva (D-AZ) has represented the district since 2003. He's collected less than 59 percent of the vote and nearly became President Obama's nominee for Interior Secretary.

But this is 2010. And this is Arizona. And after the Arizona state legislature approved its tough new anti-illegal immigration law, Grijalva asked certain minority civic and religious organizations boycott the state.

This helps explain why 28-year-old political neophyte Ruth McClung has pitched this race into the toss-up category. And McClung bolstered her bid with support from the tea party and former Alaska Governor Sarah Palin (R).

Democrats are really having to build their wall ridiculously high if even seats held by Oberstar and Grijalva are on the table.

To protect against the wave, Democrats spread shoals along the coastline, too. These are Republican-held seats that Democrats want to pick up. In other words, raising the GOP magic number for control of the House from 39 to say 45.

Democrats are poised to win a House seat in Delaware and hope to knock off Rep. Joseph Cao (R-LA) in heavily-Democratic New Orleans or Rep. Dan Lungren (R-CA). They're also focused on the seat vacated by Rep. Mark Kirk (R-IL) as he runs for Senate.

But those shoals may not be as strong as the Democrats had hoped. Even a supposedly Democratic "gimme" seat is now in question. Rep. Charles Djou (R-HI) is making a major pitch to hold his seat against state senator Colleen Hanabusa (D).

For the record, during its 51 years in the union, Hawaii voters have never turned out of office a sitting House member or senator.

In short, Democrats have tried to erect a seawall of prodigious proportion this year. They started early and nailed down some of their most-vulnerable members. But it still might not be enough as they keep having to add bricks and mortar to the top of this wall.

There are lots of high-tech gadgets that help alert people about the potential for a tsunami. But one of the most fascinating warning systems is called "animal infrasound." Prior to the 2004 tsunami in the Indian Ocean, elephants ran for the hills. Elephants have a unique aural range beyond that of humans and can hear sounds below 20 Hz all the way down to .001 Hz. The elephants heard the tsunami and got out of the way.

When it comes to the 2010 midterm elections, the Democratic donkeys were much like the Asian elephants. They detected that a tsunami was coming and began to prepare. But like those elephants, they can't track how powerful the wave might be.

All one has to do is look at the colossal size of the seawall Democrats tried to build to understand what their party faces this fall. They raised money. They got their members home to campaign. They locked down swing districts.

But a wave is coming.

"And everything we did might not be enough," said a House Democratic aide.

- FOX's Carl Cameron contributed to this report.