For years, Republicans have marveled at President Obama's success in blaming former President George W. Bush for the nation's problems, particularly its economic problems. Now, as Obama begins his sixth year in office, that success may finally be coming to an end.

Of course Obama inherited an economic mess. He deserved time to fix it. The GOP clock started at one year; after 12 months in office, would Obama own the economy? The public's answer was no, the president should be given more time.

After two years, did Obama own the economy? The answer was still no. Americans still responded positively when Obama blamed his predecessor.

After three years, the story was the same. And in 2012, Obama ran for re-election by stressing the severity of the problems he inherited and arguing that a single four-year term just wasn't enough time to fix things. He won handily.

Now Obama is starting year six in the White House. Does he finally own the economy?

Some polls suggest things haven't changed. A Washington Post survey last month found that 50 percent of those questioned said Bush is more to blame than Obama for the state of today's economy, and 38 percent said Obama is more to blame. (Seven percent blamed both equally.) The figures are pretty much the same as they were two years ago.

But Republican pollster David Winston, who works closely with the House GOP leadership, has tried to get at the question another way. The names "Bush" and "Obama" are so politically loaded that people sometimes retreat to party corners at their very mention. So Winston has been asking this instead: "Which is causing more problems in the economy? The policies of the past? Or the policies of the present?"

When Winston asked the question in November 2012, 53 percent of those surveyed said the policies of the past were causing more problems, and 44 percent said the policies of the present.

When Winston asked the same question not too long ago, in November 2013, 41 percent said the policies of the past, and 49 percent said the policies of the present.

That's a pretty significant change. Take the hot-button names out of the question, and Americans see the government's actions today as a source of current economic woes. "When you talk about policies, they've done a flip," says Winston. "It's the transition from President Obama being a solution to the current situation to his being part of the reason why the current situation exists."

What accounts for the change? Perhaps Americans simply decided that a president in his second term ought to be held responsible for the economy. In addition, the dramatic failure of the Obamacare rollout appears to have hurt Obama's image as the man in charge -- not just of health care but of the entire federal government. "Suddenly people are looking at the current situation and saying, 'You know what? Maybe he is responsible for this,' " said Winston.

Obama's new weakness is an obvious opportunity for Republicans going into November's midterm elections. But it's also a chance to misinterpret what is happening.

In 2010, when the public still blamed Bush for the economy, Republicans won a smashing midterm victory, picking up 63 seats in the House and six in the Senate. Post-election research showed the GOP won primarily because voters believed Obama, obsessed with passing his national health care bill, wasn't paying attention to their main concern, the economy.

"People were saying, 'You're off on the wrong topic,' " says Winston. "But they weren't necessarily blaming Obama for the economy." Republicans, on the other hand, focused on the economy and had a semblance of a plan, the Pledge to America, which put job creation at the top of its priority list. The result was a big win.

In 2012, Mitt Romney tried to win a referendum against Obama on the economy. The result was a big loss.

Now the GOP is working to craft a 2014 midterm strategy. They can't count on Obama to repeat his mistakes of 2010, and they don't want to repeat Romney's mistakes of 2012.

They know the public's main concern is still jobs; in remarks this week, House Speaker John Boehner made clear jobs will be the GOP's 2014 theme. But Republicans know they can't just bash Obama (although there's room for plenty of that.)

Instead, they have to have real proposals to create jobs, as well as an alternative to the mess of Obamacare. Disappointed by Obama, voters want to hear what Republicans have to offer. The opportunity is there, if the GOP is smart enough to take advantage of it.