Democrats are on the cusp of flipping 40 seats in the House, solidifying what many prognosticators had long anticipated: a blue wave.

More than two weeks after Election Day, one unresolved race in California may yet be a pickup for the Democrats.

On Wednesday, the lead enjoyed by Rep. David Valadao, R-Hanford, over Democrat TJ Cox shrunk to a slim 447 votes. Polling guru Nate Silver cast doubt on whether Hanford could maintain the advantage as ballot-counting is expected to extend into yet another week.

"We're moving [CA-21] to **Lean D**. Obviously going to be very close, but these late ballot updates keep coming in on pace with what Cox (D) would eventually need to win by a couple tenths of a point," the editor-in-chief of FiveThirtyEight tweeted.

Earlier in the week, Silver considered the race to be a toss-up, which was a downgrade from FiveThirtyEight's pre-election forecast that said the race leaned "Likely R" with Valadao having a 79-percent chance of winning.

Meanwhile, Dave Wasserman, who is the House editor of the nonpartisan Cook Political Report, called Valadao the "underdog" in his race. "T.J. Cox (D) now has a better than even chance to defeat Rep. David Valadao (R) in #CA21 and give Dems a 40 seat gain," he tweeted Wednesday evening.

Should Cox be the victor, the 40 seats Democrats will have flipped would match the upper limit of what the Cook Political Report boldly predicted just days before the midterm elections and would be the party's biggest gain in seats since the Watergate era, when they won an additional 48 seats in 1974.

Some of these Democrats faced tough odds, overcoming factors such as the recognition associated with the incumbency of their opponents and history.

For instance, Orange County, a longtime conservative bastion on the Southern California coastline, turned completely blue with the likes of Rep. Dana Rohrabacher, a 30-year incumbent, losing their races. After the midterm elections, Republicans control just 38 miles of the 2,046-mile Pacific shoreline of the contiguous United States — a far cry from the halcyon days of former President Ronald Reagan when the GOP was a force to be reckoned with on the West Coast.

Republicans also suffered tough defeats in deep-red states, including Texas and Utah, as well as in key battleground states such as Virginia and Florida, where House races and statewide contests were seen as a litmus test for President Trump.

Fundraising was another big story in the 2018 House races, where record amounts of money were drawn in for both victorious and defeated candidates. But it was the Democrats' efforts that crushed the Republicans.

Less than a month out from the election, Politico reported 92 Democratic challengers had out-raised GOP House incumbents in the third quarter. Their efforts were boosted in large part by online fundraising maven ActBlue, which drew in more than $385 million for Democratic candidates in the third quarter, according to Open Secrets.

There is some recognition among Republicans that they need a tune-up moving forward.

“I think everybody acknowledges we have a helluva problem,” Josh Holmes, a top political adviser to Senate Majority Leader Mitch McConnell, R-Ky., told Politico. “The question is whether we can get everybody to set egos and business considerations aside to solve it. I’d certainly like to try.”

Editor's note: This story has been corrected to show that Rep. David Valadao had a slim lead over TJ Cox, not the other way around.