He said Palin has an interesting biography - "Mother, governor, moose shooter. That's cool," he said - but the election should be about who can change people's lives for the better. He said that won't come from a Republican ticket that almost always supports the same positions as President Bush even though they say they will bring reform.
"I mean, you can't just make stuff up," Obama said of a new McCain ad that says Palin "stopped the Bridge to Nowhere." "You can't just recreate yourself. You can't just reinvent yourself. The American people aren't stupid."
Obama wouldn't go so far as to say McCain and Palin are lying, even when the audience tried to goad him into it, but he began showing an ad Monday that did.
"Politicians lying about their records?" an announcer asks over a shot of McCain and Palin boarding a plane. "You don't call that maverick. You call it more of the same."
McCain spokesman Tucker Bounds responded to the charges of dishonesty by saying: "Barack Obama should familiarize himself with the honest facts: John McCain and Governor Palin have actually reformed government to root out money in politics and fought wasteful spending - Sen. Obama has not."
Obama's ad was a response to the new McCain commercial called "Original Mavericks" that claims Palin stopped the bridge, a $400 million proposal to connect an island off Alaska with just 50 residents and an airport.
She originally voiced support for it during her campaign for governor, although she was critical of the size, and later abandoned plans for the project. She used the federal dollars for other projects in Alaska.
Obama said McCain's claim that lobbyists will no longer run Washington when he's president "doesn't seem very plausible."
"Sounds pretty good until you discover that seven of his top campaign managers and officials are - guess what? Former corporate lobbyists. So who is he going to tell?
"What they are going to try to do is what they always do, which is attack, go on the negative, distort, mislead, assert," Obama said, as members of his invitation-only audience of 350 began yelling "Lie! Lie!" Obama just cocked his head in response as if to say he wasn't going to go there.
Michigan has supported Democratic presidential candidates in the most recent elections, but it is up for grabs this year and is one of the few blue states Obama could be in danger of losing. Monday's stops in Flint and Farmington Hills marked his third visit to Michigan in nine days, a time when Palin's addition to the ticket has resulted in a bounce in the polls for the Republican ticket.
McCain won Michigan in the 2000 Republican primary but lost it to Mitt Romney in January, partly because of his unapologetic assessment that not all of Detroit's lost auto industry jobs would be recovered.
Obama never competed in the state during the primaries as the national party punished Michigan and Florida for holding early contests, stripping them of their delegates. The Democratic presidential candidates largely bypassed the states.
The automotive manufacturing state has been especially hard hit by the economic downturn, and Obama spoke in front of fuel efficient hybrid vehicles that he says he would help Michigan produce to create jobs. The Illinois senator stoked frustrations among residents of the Flint area where the unemployment rate is more than 12 percent - double the national average.
"You don't have to tell the people of Flint or the people of Michigan that our economy is not in good shape," Obama said to shouts of "Yeah!" from the audience. "You do need to tell John McCain - because just a few weeks ago he said the economy was fundamentally sound."
Obama said McCain can't bring change when he votes with President Bush so often.
"It's kind of hard to believe that `I'm going to change us from us,"' Obama said. He later laughingly labeled McCain's campaign the "No Change Express," a play on its slogan as the "Straight Talk Express."
