"It will be interesting to watch this debate between John McCain and John McCain," Obama said as he campaigned in Indiana with Sen. Evan Bayh, widely considered a top-tier candidate for running mate.
When asked about the air-pressure issue during an appearance Tuesday night, McCain said: "I agree with the American Automobile Association. We should all inflate our tires." Obama had noted that keeping tires inflated and cars tuned was endorsed by both NASCAR and AAA and should be part of any comprehensive plan to reduce reliance on imported oil.
However, McCain had spent recent days ridiculing Obama's remarks about tire pressure, telling a motorcycle rally in Sturgis, S.D.: "My opponent doesn't want to drill, he doesn't want nuclear power, he wants you to inflate your tires." The Republican National Committee, meanwhile, poked fun at the idea, sending reporters tire gauges with "Obama Energy Plan" emblazoned on the side.
The two rivals have been sparring for several days over energy.
Assailing his rival's energy plans, Obama said, "that's a debate I'm happy to have. Because Senator McCain's energy plan reads like an early Christmas list for oil and gas lobbyists. And it's no wonder - because many of his top advisers are former oil and gas lobbyists."
Obama's joint appearance with Bayh led to considerable speculation that Obama might announce a decision about his choice for vice president. But it was not to be.
Bayh said Obama would bring "a breath of fresh air" to the nation's capital. He said McCain "is not a bad man," but that McCain had some bad policies.
Bayh opened his introduction of Obama by saying he had some "good news" to depart. "In five short months, the Bush administration will be done," Bayh said. A McCain victory, he said, would mean "four more years of what we've had."
Bayh, a former two-term governor and son of former Sen. Birch Bayh, is a former supporter of Hillary Rodham Clinton, has executive experience and sits on the Senate Armed Services and Intelligence committees. Furthermore, Democrats view Indiana - which has not voted for a Democrat for president since 1964 - as competitive this year.
Later, the two made a campaign stop at Schoop's diner in Portage, Ind., where both shook hands. Obama ordered four cheeseburgers to go "with the works" and brushed aside questions on whether he might select Bayh as his running mate.
CBSNews.com tracks the veepstakes buzz and ranks the top contenders.
"We're in Indiana, we're campaigning with the most popular politician in Indiana," Obama said. Bayh, asked by a local reporter about the vice presidential speculation, said tersely, "Don't get me in trouble."
"[Is] he your vice president?," one woman asked Obama during a brief stop at Schoops Diner where the two senators campaigned together, reports CBS News' Maria Gavrilovic.
"I haven't made a decision about my vice president yet," Obama replied and walked off to meet with other patrons. Several reporters pressed Bayh as well, but he wouldn't budge.
Click here to read Gavrilovic's post in the "From The Road" blog.
Obama campaigned in Indiana as his campaign released a new television ad that seeks to link McCain to President Bush and questions whether McCain is the political maverick he claims to be. It shows McCain acknowledging that he agrees with Mr. Bush on most issues.
The ad also criticizes McCain on three economic issues of concern to middle-class voters: tax breaks for the wealthy, money for oil companies, and tax breaks for companies that send jobs overseas. The ad ends with a smiling McCain and Mr. Bush side by side.
McCain's campaign turned out an ad Tuesday in the other direction, suggesting that McCain differs from Mr. Bush and the GOP on important issues - without mentioning Mr. Bush by name.
In his appearance here, Obama also questioned McCain's claim to being a maverick.
While the Arizona senator has broken with his party on many issues in the past, he "reversed himself on position after position" to secure his party's nomination, Obama asserted.
"That doesn't meet my definition of a maverick."
McCain's campaign "ran an ad saying Washington is broken. No kidding. It took him 26 years to figure it out," Obama said.