House Democrats made history this month by posting significant gains in two successive election cycles — and the victories this year largely came in districts where President-elect Barack Obama didn’t do all that well, according to a new Democratic Congressional Campaign Committee analysis of the Nov. 4 results.

“A lot of people did not focus on the fact that in order to win a lot of these seats, we had to win a lot of votes” from supporters of Sen. John McCain (R-Ariz.), DCCC Chairman Chris Van Hollen (Md.) said in an interview on Monday.

With Van Hollen set to deliver the committee’s biennial election postmortem to the House Democratic Caucus this week — possibly as early as today — committee officials are claiming that their early groundwork played an important role in putting so many unlikely districts into play.

“You really do need to have a broad playing field, because you don’t know where these races are really going to materialize until late in the cycle,” Van Hollen said.

On the heels of picking up 30 seats in 2006, House Democrats picked up another 24 this cycle — including two in special elections earlier this year. Heading into the 111th Congress, Democrats now control 256 House seats to Republicans’ 175. Three districts are still up for grabs: Ballots have not been completely counted in California’s 4th district and Ohio’s 15th district, and a close December general election is forecast in Louisiana’s GOP-leaning 4th district. Louisiana’s 2nd district is expected to vote overwhelmingly Democratic next month.

Of all the Democratic pickups this year, only three were in districts that Sen. John Kerry (D-Mass.) carried in the 2004 White House election: Connecticut’s 4th district, where former investment banker Jim Himes ousted Rep. Christopher Shays, and New Mexico’s 1st and New York’s 25th districts, where Democrats won open seats.

Van Hollen praised victorious Democrats for figuring out how to prevail in challenging districts. He cited Idaho’s 1st district, Alabama’s 2nd district and Maryland’s 1st district as places where his party’s candidates faced long odds.

“They had to create an identity for themselves that was separate and distinct from the national Democratic ticket,” he said.

But the DCCC can also claim credit, Van Hollen said, for successful recruiting efforts and early attempts to set up field and media operations ahead of the presidential campaigns, “to cut out the clutter.”

According to the DCCC, the House Democratic candidate performed better than Obama in 42 competitive districts, while Obama did better than the Democrat in 14 districts. The data are not fully available in 11 additional competitive districts.

A DCCC analysis of the breakdown of House seats illustrates just how dramatic the Democratic inroads in traditional Republican areas have been. In the East, Democrats now hold 68 seats to the GOP’s 15. In the Midwest, Democrats have a 50-to-40-seat advantage, with the Ohio seat still in play. In the South, Republicans have an 86-76 seat edge, with the one Louisiana contest yet to be settled. And in the West, Democrats have a 63-34 advantage, with the California race still not called.

Despite the Democratic euphoria now, Van Hollen is warning his colleagues not to take anything for granted in the upcoming election cycle — especially now that he has signed up for a second go-round as head of the DCCC, through 2010.

“We are all realists here,” he said. “The reality is we’ll be working hard to hold on to the gains that we made. This is a cycle where we face a lot of risks.”

Van Hollen was philosophical about the four freshman Democratic incumbents who were defeated on Election Day: Rep. Tim Mahoney (Fla.) was undone by a sex scandal; Rep. Nancy Boyda (Kan.) refused financial help from the DCCC; Rep. Don Cazayoux (La.), who won a special election earlier this year, was damaged by an African-American Independent candidate; and Rep. Nick Lampson (Texas), Van Hollen said, “was running in the toughest district in the country.”

Van Hollen said House Democratic leaders are determined not to let any vulnerable incumbent go underfunded in the 2010 cycle, and he said he expected the DCCC’s “Frontline” program to be far more robust than it was in this cycle.

But looking back, he said that in contrast to 2006, Democrats did everything they could to pump money into their most competitive races.

“This time,” he said, “there’s no race where we look back and say, ‘If we had done more, it would have turned out differently.’”