WASHINGTON (AP) -- President Barack Obama and his Republican rivals are focusing on economic inequality as an issue in the 2012 campaign as they argue about which of them can best help the middle class.

It comes as studies have shown a widening gap between rich and poor, even as unemployment remains stubbornly high.

Obama has called boosting middle-class opportunity "the defining issue of our time," but former Massachusetts Gov. Mitt Romney accuses Obama of "class warfare."

There are risks for Obama and the GOP in the debate. Obama could get blamed because his economic policies haven't solved the country's problems in his first term.

On the other hand, voters agree with Obama that taxes should rise on the very wealthy.