Other elements of the budget plan would cut projected spending for Medicaid, which provides health care for the poor, as well as food stamps, student loans and other social programs that Obama and Democrats have pledged to defend.

In all, it projects spending cuts of $5.3 trillion over a decade and would cut future projected deficits substantially. Romney, too, has proposed ambitious cuts in federal spending, but without the specifics that make Ryan's plan so attractive to fiscal conservatives and such a target for Democrats.

Republicans say Ryan could help put Wisconsin, which traditionally has voted Democratic in presidential campaigns, in play and that the Catholic Midwesterner also could appeal to blue-collar voters whom Romney, a Mormon and multimillionaire, has struggled to reach in Iowa and elsewhere.

Obama's campaign had no plans to start running new television ads in Wisconsin following Ryan's pick. Officials said they didn't think Ryan was popular enough statewide to swing Wisconsin toward the Republican ticket.

Obama's campaign argues Ryan's budget could be a powerful campaign tool for the president n states like Pennsylvania and Iowa, in addition to Florida and Ohio.

Down ballot, party leaders hoped to work in tandem with Obama to turn the Ryan budget into a litmus test in congressional races, forcing Republican opponents to take ownership of the plan. The campaign arm of the House Democrats, for example, was urging its lawmakers to call Ryan's budget plan — not the man himself — Romney's new "running mate."