In his first public comments on the new Republican vice presidential candidate, President Obama today described Paul Ryan as the "ideological leader" of the Republican Party.

Obama told donors in Chicago that Ryan is "a decent man" and "an articulate spokesman" for the vision of GOP presidential candidate Mitt Romney, "but it's a vision I fundamentally disagree with."

STORY: Romney taps Ryan as his running mate

The audience in Chicago initially booed the mention of Romney, but the president cut them off, calling the Wisconsin congressman "a family man."

"I know him," Obama said of Ryan. "I welcome him to the race."

Romney spokesman Ryan Williams accused Obama of running a "fear and smear campaign because his policies have failed."

The president cited Ryan after criticizing what he called "top down" approach to economics, saying it is "central to Governor Romney and it is central to his running mate."

He added:

"Just yesterday, my opponent chose his running mate, the ideological leader of Republicans in Congress -- Mr Paul Ryan. I want to congratulate Mr Ryan. I know him, I welcome him to the race. He is a decent man, he is a family man, he is an articulate spokesman for Governor Romney's vision but it is a vision that I fundamentally disagree with."

The full statement from Romney spokesman Williams: