Democrats on Monday will start attacking the Republican majority in the House with radio ads airing in 25 Republican-held districts — the same number Democrats need to flip in 2012 to take back control of the House.

Republican Reps. Steve King (Iowa), Dan Lungren (Calif.), Vern Buchanan (Fla.), Sean DuffySean DuffyJuan Williams: Trump and the new celebrity politics Lewandowski urges Trump, Kelly to fire head of Consumer Financial Protection Bureau These 5 House Republicans are ripping their Senate colleagues over healthcare MORE (Wis.) and Joe Heck (Nev.) are among the 25 Republican incumbents to be targeted.

The Democratic Congressional Campaign Committee is not disclosing the size of the buy, but will air the ads for one week, and will augment the "Drive for 25" push with Web ads and a telephone campaign.

“With one year to go until the election, the House Republicans’ majority is in peril as it gets freezing cold back at home and Republicans face a chilly response to defending the indefensible,” said DCCC Chairman Steve Israel (D-N.Y.).

Voters in some districts will hear generic ads calling their representative part of the problem with Washington and critiquing how Republicans voted on tax cuts for the wealthy and Rep. Paul RyanPaul RyanGOP chairman to discuss Charlottesville as domestic terrorism at hearing Trump’s isolation grows GOP lawmaker: Trump 'failing' in Charlottesville response MORE's (R-Wis.) budget. But some Republicans will get hit with highly tailored ads knocking them on issues that have been controversial for them in the past.

"Congressman David Rivera’s under criminal investigation for his personal and campaign spending. He spends more time defending himself than fighting for us," says the narrator in the ad targeting the Florida Republican.

The DCCC ads come as Democrats are trying to build a buzz around the prospect of wresting control of the House back from Republicans in 2012, despite widespread concerns that President Obama's unpopularity could imperil Democrats up and down the ticket.

House Minority Leader Nancy Pelosi (D-Calif.) told reporters on Thursday that Democrats "have definitely put the House in play," touting their recruitment efforts and talking up their fundraising, which has exceeded that of House Republicans in recent months.

But Republicans point to GOP gains from redistricting in districts that went for Obama in 2008 and the beleaguered economy that Republicans blame squarely on the Democrats. House Speaker John BoehnerJohn BoehnerIt's time for McConnell to fight with Trump instead of against him How Republicans can bring order out of the GOP's chaos Republican donor sues GOP for fraud over ObamaCare repeal failure MORE (R-Ohio) said Thursday he was certain the GOP would hold on to the House.