Democratic leaders fighting an uphill battle to retake the House this fall say they got a huge boost when Mitt Romney picked Rep. Paul RyanPaul RyanGOP signals infrastructure bill must wait Oil concerns hold up Russia sanctions push Overnight Finance: Pressure builds for GOP on taxes | NAFTA talks to begin in August | DOJ expands asset seizure program | Regulator defends charters for financial tech firms MORE (R-Wis.) as his running mate.

Democrats have hammered Ryan's spending bills since he first proposed steep cuts to Medicare benefits last year as head of the House Budget Committee. Ryan's ascension to vice presidential nominee only highlights those proposals, the Democrats say, making it easier for their party to attack the GOP's plans for Medicare — and tougher for Republicans to distance themselves from them.

"Gov. Romney embraced the repeal of Medicare [by picking Ryan]," House Minority Leader Nancy Pelosi (D-Calif.) told reporters in the Capitol on Thursday. "That was a sad day for our country and for Medicare, but at least it put the focus on the issue.

"I guess he was catering to his base, but whatever he thought was a good idea at the time ranks along there with some of his other poor judgment," she added. "I've always been optimistic [about winning the House], but, yeah, I'm more optimistic [now]."

Rep. Steve Israel (D-N.Y.), the head of the Democratic Congressional Campaign Committee (DCCC), was even more direct in assessing Ryan's rise to VP contender.

"Ryan has become a down-ballot disaster for Republicans across the country," Israel said Thursday in his first update on the House outlook since Congress returned from its long August recess. "We have House Republicans who put their voting card in the machine and voted 'yes' to end Medicare as we know it. You may be able to muddle [that message] at one level, but you can't muddle it when you have a vote you can hang around people's necks. And we have that vote."

Israel all but thanked Romney for his pick.

"Mitt Romney grabbed the megaphone from us when he chose Paul [Ryan]," he said. "He branded this debate, and gave us the debate we wanted."

Ryan has introduced two budgets in the two years since the Republicans took the House. The 2012 proposal, introduced last year, would privatize Medicare for those entering the popular seniors healthcare program a decade from now. 

The more recent version, passed this spring with near-unanimous support from House Republicans, would keep traditional Medicare as an option while capping the dollar amount the federal government would provide for premiums. 

The Congressional Budget Office estimates seniors would pay $6,400 more each year under the latest proposal.

Israel said Republicans in 2010 were swept into control of the House "on a Tea Party tsunami," but he noted that the political environment has changed since then.

"The wave has receded, and they are left high and dry with their voting records," Israel said. "We're not going to let them escape from their voting records."

The DCCC chairman noted that Ryan's budget played a big role in Democratic Rep. Kathy Hochul's surprise victory in a New York special election last year. Hochul wasn't given much of a chance against Republican Jane Corwin in the state's conservative 26th district. But her numbers soared — and Corwin's plunged — when Hochul focused the contest on Ryan's plan to scale back Medicare benefits.

"We believe she'll win again on that message," Israel said.

Still, Israel and the Democrats have a tough road ahead. After gaining control of the House in 2006 and picking up more than 20 additional seats in 2008, Democrats were trounced at the polls in 2010, losing 63 seats and handing the gavel to Rep. John BoehnerJohn BoehnerSudan sanctions spur intense lobbying OPINION | GOP's 7-year ObamaCare blood oath ends in failure A simple fix to encourage bipartisanship in the House MORE (R-Ohio) and the Republicans. To retake the lower chamber in November, Democrats would need to pick up at least 25 seats — a heavy lift amid a limping economy and a neck-and-neck presidential contest.

Israel on Thursday said the 25-seat figure is in reach, arguing that the Democrats "clearly won" the month of August and now have the momentum heading into the final weeks before November. But Israel declined to predict how many seats the Democrats would ultimately pick up in November.

"I don't know," he said. "The winds are shifting."

Israel conceded that the factors shifting those winds rest largely outside the Democrats' control. Indeed, the three episodes Israel cited as contributing most to the Democrats' August gains — Romney choosing Ryan, Rep. Todd Akin's (R-Mo.) controversial comments on "legitimate rape" and a flap surrounding an alcohol-soaked GOP trip to the Sea of Galilee last summer — all fit that category.

"A lot of what happens is out of our control," he said. "What's in our control is how we grab those fumbles and run the ball in the opposite direction toward our goal. And it's worked."

Pelosi, for her part, said Romney's pick of Ryan has helped the Democrats' cause.

"We were going to make this fight anyway, we saw this as essential," Pelosi said. "Gov. Romney is making it easier ... by embracing the repeal of Medicare."

— This story was first posted at 1:03 p.m. and has been updated.