WASHINGTON, May 22 (AP/UNB) - President Barack Obama's and Republican challenger Mitt Romney's starkly differing visions of how the U.S. economy should work are drawing into sharper focus as the candidates appeal to voters who say jobs and economic security are the foremost issue in the November election.

Obama's attacks on Romney's tenure as head of a successful private equity firm and a determination "to maximize profits" are an assault on free enterprise, Romney says.

The president says the drive for profit is "not always going to be good for communities or businesses or workers."

The Obama campaign has tried, in a recent ad and an online video, to undermine Romney's record as a business executive by focusing on two companies that were closed down or failed after they were absorbed into the web of enterprises under Bain Capital, the organization Romney helped found in 1984. He maintains financial ties to the company but left it years ago to run the Salt Lake City Olympic games and then to serve as Massachusetts governor.

Obama's remarks Monday at the end of a NATO summit in Chicago were in response to a question about Newark, New Jersey, Mayor Cory Booker's weekend criticism of the Obama campaign's attack on Romney's private equity background. Booker, an Obama supporter, called exchanges by the campaigns over Bain "nauseating" and a distraction from issues that interest voters.

"This is not a distraction," Obama said at a news conference. "This is what this campaign is going to be about."

The increasingly strident argument about the economy took place against the background of a new poll that shows Obama and Romney running nearly even.

The Washington Post-ABC News poll released late Monday found voters split 49 percent for Obama and 46 percent for Romney. On handling the economy, they are tied at 47 percent.

The survey found that 80 percent of Americans still hold a negative view of the economy, but 54 percent said they felt more positively about the economic situation in the coming years, and 58 percent felt the financial prospects would improve.

The Obama campaign's line of attack illustrates the president's complicated relationship with the business community. He has used populist language to attack Wall Street executives and bankers as "fat cats" and called for an end to tax subsidies for oil and gas companies, but he also expanded the government's rescue of the auto industry and has promoted tax breaks for small businesses.

While some of his Wall Street support has waned, he still draws a significant amount of campaign contributions from major investors, retaining a good relationship with, among others, billionaire investor Warren Buffett.

Romney's campaign has welcomed the debate on jobs.

"President Obama confirmed today that he will continue his attacks on the free enterprise system, which Mayor Booker and other leading Democrats have spoken out against," Romney said Monday. "What this election is about is the 23 million Americans who are still struggling to find work and the millions who have lost their homes and have fallen into poverty. President Obama refuses to accept moral responsibility for his failed policies. My campaign is offering a positive agenda to help America get back to work."

While the economy has begun to recover under Obama, unemployment remains above 8 percent. His challenge is persuading voters to stick with him while withstanding criticism from Romney that his policies have hindered the recovery.