The Romney campaign on Wednesday mocked President Obama for putting out a glossy 20-page booklet laying out his second-term economic plan, describing it as a collection of recycled ideas two weeks before Election Day. 

Obama, meanwhile, returned to accusations at a campaign stop in Iowa that his Republican rival's tax plan serves the wealthy and would "stick the middle class with the bill." 

The exchange marked the opening of a marathon campaign blitz for the president, who is embarking on the busiest travel day of his 2012 campaign. The president is planning to hit five states by Thursday morning, covering 5,300 miles. 

He was going from Washington to Iowa, Colorado, California and Nevada, and then overnight to Florida. It was the first time Obama was spending the night flying on Air Force One for a domestic trip but far from unprecedented by incumbents scrambling to keep their job. 

The president on Tuesday, responding to criticism that he's spent too much time criticizing Romney and not enough time talking about what he'd do in a second term, released a 20-page booklet focusing on his second term jobs agenda. The "Blueprint for America's Future" outlined his proposals and promised to distribute millions of copies. The plan includes spending more on education, boosting U.S. manufacturing jobs and raising taxes on top earners. 

But Romney spokeswoman Andrea Saul dismissed the move. 

"With two weeks left, President Obama is kicking off yet another campaign tour and touting his 20-page brochure that he's calling an agenda," she said. "But instead of a positive vision for a second term, the president is only offering voters four more years like the last four years, with $2 trillion in higher taxes, over 700,000 fewer jobs, and $716 billion in Medicare cuts." 

Both men are making extraordinary efforts to sway the small pool of undecided voters while imploring their millions of supporters to vote, particularly in key battleground states such as Ohio and Iowa where early voting is already under way. 

Obama planned a short stop in Chicago on Thursday to cast his own vote -- the first time an incumbent president has opted for early voting. 

The election map has shrunk to no more than nine of the 50 U.S. states, and that's where both candidates will be spending virtually all of their time in the final days before the election. 

Residents in those so-called battleground states do not reliably vote either Republican or Democrat. The states assume outsized importance because the president is chosen according to state-by-state contests, not the national popular vote. 

Obama will break for an appearance Wednesday on "The Tonight Show with Jay Leno" and make calls to voters from the plane. 

Romney, too, was picking up the pace. He was campaigning Wednesday in Nevada and Iowa before a three-stop campaign in Ohio on Thursday. 

Romney told a crowd of 10,000 supporters on Tuesday that Obama's promise of more of the same is "why he's slipping and it's why we're gaining." 

Obama's campaign insisted that the president was holding on to a slight lead in most of the nine battleground states -- Nevada, Colorado, Iowa, Wisconsin, Ohio, Virginia, North Carolina, Florida and New Hampshire 

The Associated Press contributed to this report.