COLUMBUS, Ohio (AP) -- President Barack Obama launched a new phase of his re-election campaign on Saturday by branding GOP challenger Mitt Romney as an eager rubber stamp for extremist Republicans in Congress and offering himself as a hard-charging champion of an embattled middle class.
In the first formal rallies of his bid for a second term, Obama acknowledged the U.S. economy has struggled to recover from a painfully deep recession but declared, "We've been through too much to turn back now."
Obama's toughly worded speech at a noisy basketball arena at Ohio State University previewed a similar event later Saturday at Virginia Commonwealth University in Richmond. Both states are shaping up as among the most hotly contested states of the 2012 campaign.
At Ohio State, Obama was introduced by first lady Michelle Obama, who called her husband an "awesome" president and someone who understands the struggles of average Americans.
The president said those struggles are central to his re-election bid.
"For the last few years, the Republicans who run this Congress have insisted that we go right back to the policies that created this mess," Obama said, even though Democrats control the Senate. "But to borrow a line from our friend Bill Clinton, now, their agenda is on steroids."
Obama listed more top-end tax cuts and cuts to education and Medicare as among GOP priorities.
"After a long and spirited primary, Republicans in Congress have found a nominee for president who has promised to rubber stamp this agenda if he gets a chance," he said to jeers from the young crowd. "We cannot give him that chance. Not now. Not with so much at stake."
Obama said seems to believe if wealthy Americans like him or big corporations get richer, the country will prosper. But he said bigger profits haven't led to better jobs, and Romney "doesn't seem to get that."
Obama also taunted Romney's primary season observation that "corporation are people, my friend."
Said Obama: "I don't care how many ways you try to explain it. Corporations aren't people. People are people."
The campus events were billed as the official kickoff of Obama's re-election bid, even though he's been solidly engaged in his campaign and over a year ago filed the necessary paperwork to run again.
He's headlined dozens of fundraisers around the country as his campaign tries to build a solid money advantage over Romney. In his official White House travels, often to the most contested states, the president has pitched policy positions that fit neatly into the campaign's central theme of economic fairness. They range from a millionaires' tax to freezing student loan interest rates.
Official campaign rallies can free Obama up to take more direct aim at Romney. Until now, Obama has used Romney's name sparingly, often choosing instead to cloak his criticisms of Romney in attacks against generic Republicans.
Some Democrats saw the events as a chance for Obama to put Republicans on notice that he plans to be an aggressor in the race.
"What we've seen too many times in the past is Democrats are way too meek in defining their opponents or defining themselves in an election," said Maria Cardona, a Democratic strategist. "This president is not going to let the Republicans define him."
But campaign officials said Obama's twin appearances were not a campaign re-launch.
David Axelrod, a senior adviser, said the president wasn't a candidate who "reinvents himself week to week" -- a jab at Romney's sometimes shifting positions.
Republicans argue the Obama campaign is not aiming for consistency, but rather struggling to find a comprehensive vision for a second term.
"They have nothing positive to run," said Sean Spicer, communications director for the Republican National Committee. "No successful incumbent, no impressive record and no thriving economy."
New job numbers on Friday highlighted the challenge Obama. Job growth slumped for a second straight month. The unemployment rate dropped to 8.1 percent in April, but largely because more people stopped looking for work and therefore were no longer deemed unemployed.
In the face of continued economic unease, Obama's campus rallies were intended to recapture some of the youthful, hopeful energy of his 2008 campaign -- and target a voting bloc, young people, that was crucial to his victory.
His choice of states was equally telling.
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. Both Obama and Romney advisers acknowledge that the state is up for grabs.
During a campaign event in Portsmouth, Va., on Thursday, Romney said, "This may well be the state that decides who the next president is."