SPRINGFIELD, Ill. — Delaware Sen. Joe Biden took on the role of Democrat Barack Obama's new presidential running mate yesterday, attacking Republican candidate John McCain and making clear that whatever doubts he'd previously expressed about Obama's readiness were gone.

In a joint appearance with Obama 12 hours after Obama announced that Biden was his choice for vice president, Biden called Obama an inspiration to millions with "steel in his spine" and "a clear-eyed pragmatist who will get the job done."

He went after McCain, a longtime personal friend, as having given "in to the right wing of his party and yielded to the very Swift Boat politics he once so deplored."

He also said McCain would continue President Bush's policies. And he chided that McCain is so wealthy and insulated from average people's concerns that his version of making difficult kitchen-table decisions is that "he'll have to figure out which of his seven kitchen tables to sit at."

Democratic leaders embraced Biden's selection, noting that Biden has served in the Senate for 35 years and has been both chairman of the Judiciary Committee and of the Senate Foreign Relations Committee.

GOP: PICK HYPOCRITICAL

The Republican Party line was to call the choice hypocritical, highlighting Biden's campaign contributions from special interest groups whose influence Obama says he wants to reduce and Biden's early assertions, when he was competing with Obama for the nomination, that Obama wasn't ready for the job.

But some of Obama's Republican friends praised Biden, including Sens. Chuck Hagel of Nebraska and Indiana Sen. Dick Lugar.

Obama introduced Biden before a crowd estimated at 35,000 outside the Illinois Old State Capitol.

In Springfield, reaction to Biden ranged from enthusiastic to curious.

"This was by far the best choice," said Russ Breckenridge, 31. "He strengthens Barack's foreign policy experience and can attack John McCain like Barack can't because Barack is the kind of individual that believes in being above the fray."

Judi Gentry, 68, had liked Virginia Gov. Tim Kaine's moderate, pro-life, outside-Washington image. "I would really have like another fresh face there," she said. But she said she trusts Obama's choice with the 65-year-old Biden. "I guess this is what he has to do to combat the constant attacks of 'he's too young, too inexperienced.' "