CHICAGO (Reuters) - President Barack Obama on Sunday launched his opening salvo against Paul Ryan, whose emergence as the Republicans' vice presidential candidate gives the Democrats a chance to target their rivals as uncaring.
The architect of a budget plan that would make deep cuts to the U.S. social safety net, Ryan will be portrayed by the Obama campaign as a threat to the elderly and the poor.
But to do that, the Democrats must sharpen their attacks, which have been most successful when focused on Republican presidential hopeful Mitt Romney's business past and personal finances rather than policy.
And in Ryan, the Obama team have an opponent who is an economics expert recognized even by Democrats as a budget heavyweight.
Obama dubbed Ryan on Sunday as the "ideological leader" of congressional Republicans who is bent on imposing "top-down economics" on middle-class Americans.
"He's a decent man. He is a family man. He is an articulate spokesman for Governor Romney's vision. But it's a vision that I fundamentally disagree with," Obama told a fundraiser in Chicago.
He spoke over boos from some in the audience at the mention of the Wisconsin congressman's name.
The remarks were Obama's first comments about Romney's selection of the conservative as his running mate, which has injected new energy into the Republican campaign.
Democrats will try to scare independents, senior citizens, and liberal voters over the lawmaker's controversial cost-cutting proposals like reforms to Medicare.
Bill Burton, who runs Priorities USA Action, a "Super PAC" group that backs Obama, said his team had planned to feature the Ryan budget in ads this fall long before Romney made its architect his running mate on Saturday.
"In our first focus groups we saw how toxic the Ryan plan was, but the problem was trying to get voters to believe that a politician could possibly support it," Burton said.
He cautioned that the economy was still weak and Romney would have hundreds of millions of dollars at his disposal to spend on ads in the campaign.
The Democratic strategy of highlighting Ryan's budget plan carries risks.
Ryan could win a reputation with undecided voters for boldness in at least trying to tackle the huge budget deficit.
The Romney campaign will remind Americans of stimulus spending under Obama and cast the fiscal issue as a fight between Ryan's plans and wasteful big government.
"If we handle it right, it can backlash on them," said Charlie Black, a Republican strategist who has advised Romney's and Senator John McCain's presidential campaigns.
Black said Republicans, who are already trying to nail Obama for the high unemployment rate could knock him further for not addressing fiscal issues.
"There's been no effort whatsoever on the part of the administration to address the looming crisis of Social Security and Medicare," McCain said on Fox News Sunday.
Obama campaign officials said the Ryan choice was a direct appeal to the Republican base and a reaction to pressure from the right wing of his party, which has not been convinced by Romney.
"It's a base move," said one senior Obama campaign official in an email, acknowledging that the selection would energize social conservatives and probably make the Republican convention later this month more harmonious.
Reporting by Jeff Mason; Editing by Alistair Bell