Republicans and their allies are keeping up the pressure on vulnerable Democratic lawmakers early in the campaign cycle.

Crossroads GPS, the group conceived of by GOP strategists Karl Rove and Ed Gillespie, announced Wednesday that it's purchased $450,000 worth of radio airtime, the bulk of which is in a dozen Democratic-held swing districts.

The group's ad targets Democrats who voted against the Republicans' continuing resolution (CR), the funding measure passed by the House on Saturday that cuts $61 billion from current spending.

Opening with a quote from the late President Ronald Reagan, the Crossroads ad talks about the "explosive growth of government."

"Members of Congress like Joe Donnelly voted to continue the failed spending policies of Pelosi and Obama. They just don't get it," the announcer says in the minute-long ad. Indiana's Donnelly edged out his Republican challenger in 2010 with 1 percent of the vote.

The group's largest expenditure — more than $63,000 — is in New York's 1st district, where Rep. Tim Bishop (D) squeaked out a reelection victory almost a month after Election Day. The group also purchased airtime in 10 Republican-held swing districts thanking the members for their vote on the CR.

Meanwhile, the National Republican Congressional Committee followed up the release of its first TV ad earlier this week with a round of auto-calls in the districts of 10 "vulnerable Democrats," according to a release. Utah Rep. Jim Matheson (D), who was on the receiving end of the TV ad, also gets hit with the call.