WASHINGTON - With Republicans distracted by an increasingly divisive primary battle, President Obama and his aides have begun a high-stakes effort to change how voters look at the main issue in the 2012 election - the nation's continued economic troubles.

Republicans would like to make the Nov. 6 election a referendum on Obama's economic record. For much of his presidency, they have pounded away at monthly statistics showing high unemployment and anemic growth.

"We're seeing continuing high levels of unemployment. We see home values declining; foreclosures remain at record levels," former Massachusetts Gov. Mitt Romney points out often. Obama, he says, "has failed in the job he was elected to do."

Until recently, the main Democratic response was that although Obama's stimulus plan and other measures had not cured the economy, they had averted another Great Depression. But party strategists concede that as a slogan, "could have been worse" is more likely to win support among economists than average voters.

So, increasingly Obama and his aides have switched to a longer view, trying to focus attention on what they portray as his defense of the middle class. That positioning, they hope, will set up a helpful contrast with his November opponent.

"This isn't just about recovering from this recession," said a senior adviser to Obama, one of several who spoke on condition of anonymity because they were not authorized to speak publicly about internal White House discussions. "This is about saving the middle class from a decline that's been going on for three decades."

Obama began to highlight the shift this month, and it may already have helped him when combined with a somewhat warmer economy and Republican disarray. Public approval of Obama, which in late summer had fallen below 40 percent in at least one major poll, has now approached 50 percent in several surveys.

"It's a much stronger position than where he was before," said Democratic pollster Stanley Greenberg. In a closely divided electorate, shifting by a few points "matters substantially, and it reflects a sustained change in the narrative" from Obama. Talking about the "state of the middle class" connects with voters in a way that discussing the "state of the recovery" does not, he said.

Aides expect that the new way of framing economic issues will figure heavily in the Jan. 24 State of the Union speech. Obama aims to tie every new initiative he floats next year back to that idea, they add.

The theme carries risk for Obama. It plays against the usual voter focus on immediate economic concerns rather than long-term trends. Especially if the economy slows again, Republicans could accuse Obama of trying to duck the problem of creating jobs.

In a Wall Street Journal column Thursday, Karl Rove, former chief strategist to President George W. Bush, pushed that line of attack as he accused Obama of "pretending the past three years are someone else's responsibility."

But the idea also has a large potential upside. If the economy keeps improving, better news could blunt GOP attacks. And Democrats will have hardened the idea of the election as a choice between the candidates, not simply a referendum on Obama. The theme of giving the middle class a "fair shot" potentially works against whoever survives the demolition derby among the Republican candidates, all of whom share essentially the same economic views.

The "fair shot" theme also provides a more positive message than previous Obama formulations, which some analysts saw as harder-edged attacks on the wealthy.