The choices voters face in November isn't "just a choice between two candidates ... . [This} is a choice between two fundamentally different visions of this country," Obama said. "The direction you chose ... will impact your lives and your children's lives for decades to come."
Interrupted frequently by applause and chants of "Four more years," Obama said the 2012 election was about restoring "the basic bargain that made this country great" of getting ahead if the country pulls together, everyone has a fair shot and everyone plays by the same rules.
"That's the American promise," Obama said. "That's the American dream."
The remarks came as Obama opened his three-day bus tour of the Hawkeye State.
Work still needs to be done to right the American economy, he said, adding it would take more than "one year, one term and possibly one president."
While saying he liked Rep. Paul Ryan, the Wisconsin congressman picked by presumptive Republican presidential candidate Mitt Romney to seek the Republican nomination for vice president, Obama said Ryan, as House Budget Committee chairman, is the architect of the GOP vision to move the country forward.
"The problem is, that vision is one I fundamentally disagree with," Obama said, ticking off Republicans' desires to end more regulations on big corporations, provide tax breaks for the wealthy and make Medicare a voucher system.
Republicans have "tried to sell the trickle-down [economic] theory before" and it didn't work "and it won't work now," Obama said.
Obama pointed to the differences between him and Romney on the housing crisis, the auto bailout and whether to extend tax cuts enacted during George W. Bush's administration for all, or allow tax cuts for the wealthy to return to the levels seen during Bill Clinton's presidency, as well as rescinding the Affordable Care Act, also known as Obamacare.
"It's true, Obama does care -- that's why we passed this bill," the president said. "The Supreme Court has spoken; we are not going backward, we're going forward."
All of the issues are part of what makes up middle-class life and all are bound together, he said.
"You are going to see other side spend more money on negative ads than ever seen in American history," he warned. "They're going to say the same thing over and over again: The economy not as good as should be and it's Obama's fault."
"But when you come together and reaffirm the core values that make this country greatest country in the world ... you can't be stopped," Obama said. "That is what is at stake for this election, not just for me, but for this country that we believe in."