Democrats have been saying for a long time that control of the House of Representatives could be in play in 2012, and some Republicans are starting to agree with them.

Former congressman Tom Davis believes that Democrats would need a wave, and that one is possible. “Continued polarization and obstruction could create such a wave,” the Virginia Republican wrote recently in an op-ed in The Hill.

Former Republican National Committee chairman Michael S. Steele agreed that keeping the majority isn’t a done deal: “It could be very, very hard.”

And last week, a member of the conservative Wall Street Journal editorial board opined that the GOP majority could be in jeopardy if Republicans don’t make it a priority.

“The House is no sure thing,” Kimberly A. Strassel wrote.

In fact, there is a growing behind-the-scenes sense among House Republican leaders that the more the presidential race has enveloped the daily news, the importance of keeping the House has been lost.

Combine that with some recent momentum for Democrats, and it’s causing some unease inside the GOP.

This is not to say that there is a consensus in the GOP that its House majority is in danger.

“I just don’t think there’s a possibility that it happens,” said former congressman Tom Reynolds (R-N.Y.), who, like Davis, is a former chairman of the National Republican Congressional Committee. “With a 25-seat majority, I just don’t think they can get that much.”

But given that the last three election cycles saw at least 24 House seats changing parties, it is not outlandish to think a 25-seat GOP majority may be endangered. In today’s electoral environment, few majorities are safe.

Democrats believe that they have reason to be hopeful, beginning with their standing in the generic ballot. This measure basically shows that, given a choice between a nameless, faceless Republican and a nameless, faceless Democrat, voters right now prefer the Democrat — and by several points in some polls.

Republicans, though, note that Democrats generally have a small advantage on this measure. “They’ve done a heck of a spin” on the generic ballot, Reynolds said. “I think the generic ballot’s something to watch, but when I was chair, if Democrats had a four-point advantage, I looked at that as even.”

Democrats also believe that the president’s new momentum will help them. After two good jobs reports in a row, President Obama’s personal approval rating rose to 50 percent in a new Washington Post-ABC News poll. On some level, the 2012 House election is really an extension of the presidential race, and for Democrats to retake the House, they probably have to keep the White House. That looks like more of a possibility today than it did Jan. 1.

On the fundraising front, the Democratic Congressional Campaign Committee actually outraised its GOP counterpart, the NRCC, by about $7 million last year, despite Republicans being in the majority. On top of that, Democratic challengers outraised more than a dozen GOP incumbents in the fourth quarter of 2011 — a strong sign of the quality of Democratic candidates.

There is some history on Democrats’ side, as well. Republicans have held this big of a majority five times since 1900, and each time they sustained huge losses in the next election — an average loss of 48 seats. But Republicans haven’t had a majority this big since the 1940s, so there’s no recent apples-to-apples comparison.

Publicly, GOP leaders have been bullish on their prospects for holding on to the House, and point to a number of issues in their favor, starting with the number of Democratic retirements. House Democrats have been bitten more by the retirement bug than Republicans — 20 Democrats are either retiring or running for higher office, compared with 14 Republicans — and their retirees come from tougher districts, too.

According to the Cook Political Report, Republicans are favored to win five districts held by retiring Democrats, and Democrats aren’t favored to win any seats held by retiring Republicans. In other words, if the GOP can win these seats, Democrats would have to win 30 seats to retake the majority.

Then there are the super PACs. Whatever advantage the DCCC has over the NRCC is likely to be wiped out — and then some — by Republican-leaning super PACs that could plug tens of millions of dollars into keeping the House.

Even if GOP leaders may not be as focused on the House as some would like, American Crossroads is essentially a second NRCC ready to put its money on the table to save the majority, and there’s no comparable Democratic equivalent.

While redistricting may not have been the windfall that the GOP had hoped, redistricting has helped Republicans shore up some of their most vulnerable members. In most cases, these members got a few percentage points better and will still have to defend themselves, but overall it’s been a boon to the GOP.

Republicans also have a historical justification for being optimistic. History shows that it’s exceedingly rare for the president’s party to win control of the House when that president is up for reelection. More often than not, the president’s party makes modest gains, if any.

Even when Ronald Reagan won a resounding reelection victory in 1984, his party gained just 16 seats. The last time a president’s party won more than 25 seats while the president was being reelected was 1964.