Romney and his "friends in Congress think the same bad ideas will lead to a different result, or they're just hoping you won't remember what happened the last time you tried it their way," the president told thousands of cheering partisans at what aides insisted was his first full-fledged political rally of the election year.
Six months before Election Day, the polls point to a close race between Obama and Romney, with the economy the overriding issue as the nation struggles to recover from the worst recession since the 1930s. Unemployment remains stubbornly high at 8.1 percent nationally, although it has receded slowly and unevenly since peaking several months into the president's term. The most recent dip was due to discouraged jobless giving up their search for work.
Romney has staked his candidacy on his ability to create jobs, but Obama said his rival was merely doing the bidding of the conservative powerbrokers in Congress and has little understanding of the struggles of average Americans.
"Why else would he want to cut his own taxes while raising them for 18 million Americans," Obama said of his multimillionaire opponent.
The president's campaign chose Ohio State University, the biggest college campus in a perennial swing state, and Virginia Commonwealth University for the back-to-back rallies. In 2008, Obama won Ohio while reversing decades of Republican dominance in Virginia. Since then, Virginia has swung back toward the GOP in statewide elections.
Obama has attended numerous fundraisers this election year, but over the escalating protests of Republicans, the White House has categorized all of his other appearances so far as part of his official duties.
He was introduced in Columbus by first lady Michelle Obama, and walked in to the cheers of thousands. While the president is notably grayer than he was four years ago, he and his campaign worked to rekindle the energy and excitement among students and other voters who propelled him to the presidency in 2008.
"When people ask you what this election is about, you tell them it is still about hope. You tell them it is still about change," he said. It was a rebuttal to Romney's campaign, which has lately taken to mocking Obama's 2008 campaign mantra as "hype and blame."
If the economy is a potential ally for Romney, Obama holds other assets six months before the vote.
Unlike Romney, who struggled through a highly competitive primary season before recently wrapping up the nomination, Obama was unchallenged within his own party. As a result, his campaign's most recent filing showed cash on hand of $104 million, compared with a little over $10 million for Romney, and has worked to build organizations in several states for months.
But in the aftermath of recent Supreme Court rulings, modern presidential campaigns are more than ever waged on several fronts, and the effect of super political action committees and other outside groups able to raise donations in unlimited amounts is yet to be felt.
Already, while Romney pauses to refill his coffers, the super PAC Restore Our Future has spent more than $4 million on television advertising to introduce the Republican to the voters.
Romney had no public events Saturday after spending much of the week campaigning in Virginia and Pennsylvania.
A campaign spokeswoman, Andrea Saul, responding to Obama's speech in Ohio, said, "While President Obama all but ignored his record over 3 1/2 years in office, the American people won't. This November, they will hold him accountable for his broken promises and ineffective leadership."
With his rhetoric, Obama belittled Romney and signaled he intends to campaign both against his challenger and the congressional Republicans who have opposed most of his signature legislation overwhelmingly, if not unanimously.
After a spirited campaign for the Republican nomination, Obama said, the GOP leadership picked someone "who has promised to rubber stamp" their agenda if he gets a chance.
Romney is a "patriotic American who has raised a wonderful family," and has been a successful businessman and governor, the president said. "But I think he has drawn the wrong lessons from that experience. He sincerely believes that if CEOs and investors like him make money the rest of us will automatically do well as well."
Scarcely more than a dozen states figure to be seriously contested in the fall, including the two where Obama was campaigning Saturday.
They include much of the nation's industrial belt, from Wisconsin to Michigan, Ohio and Pennsylvania, as well as Nevada, Colorado and, the president's campaign insists, Arizona; the latter three all have large Hispanic populations. Both campaigns also are focusing on Iowa, Florida, North Carolina, Virginia and New Hampshire. Together, those states account for 157 electoral votes.
Barring a sudden crisis, foreign policy is expected to account for less voter interest than any presidential campaign since the attacks of Sept. 11, 2001. Since taking office, Obama has made good on his pledge to end the war in Iraq, announced a timetable to phase out the U.S. combat role in Afghanistan by 2014 and given the order for a risky mission by special forces in which Osama bin Laden was killed in his hideout in Pakistan.
One recent poll showed the public trusts Obama over Romney by a margin of 53-36 on international affairs.
While the battleground states tend to be clustered geographically, the state-by-state impact of the recession and economic recovery varies.
In Ohio, for example unemployment was most recently measured at 7.6 percent, below the national average. It was higher, 9.1 percent and rising, when Obama took office, reaching 10.6 percent in the fall of 2009 before it began receding.
In Virginia, it was 5.6 percent in March, well below the national average. It was 6.6 percent in February 2009 and peaked in June of that year at 7.2.
In a measurement that shows an economy recovering, yet far from recovered, the Labor Department reported this month that 54 metropolitan areas had double-digit unemployment in March, down from 116 a year ago. By contrast, joblessness was below 7.0 percent in 109 areas, up from 62 a year earlier.
No matter the change, Romney attacks Obama's handling of the economy at every turn.
"If the last 3 1/2 years are his definition of forward, I'd have to see what backward looks like," he said late last week in Virginia.
The first lady, who accompanied the president during the day, has attended more than 50 fundraisers since his campaign filed formal candidacy papers with the Federal Election Commission 13 months ago.