It’s been a while since President Obama could fairly be described as “popular,” and his approval rating has been stuck in the mid-40s for most of the year.

But as 2011 wraps up, it appears that the president’ support is starting to grow. A new Washington Post/ABC News poll shows Obama’s approval rating at 49%, which is the highest it’s been since March, excluding the bump the president received after the bin Laden killing.

Perhaps more important to the battle over the payroll tax cut, Obama has regained an advantage over Republicans in Congress when it comes to “protecting the middle class.” In the new poll, 50 percent say they trust Obama on this issue, compared with 35 percent who choose the GOP — a major change from last month, when the two sides were more evenly matched on the question.

On taxes, Obama has improved since early October, while public trust of the GOP has slipped. Forty-six percent now side with Obama on the issue, and 41 percent with Republicans in Congress. Independents now side with the president on that front by a 17-point margin, 49 to 32 percent.

A new CNN poll was released this afternoon, and it also shows the president’s approval rating up to 49%.

“President Barack Obama’s approval rating appears to be fueled by dramatic gains among middle-income Americans,” says CNN Polling Director Keating Holland. “The data suggest that the debate over the payroll tax is helping Obama’s efforts to portray himself as the defender of the middle class.”

Obama’s gains have come at the expense of the Republicans in Congress and the GOP in general. By a 50% to 31% margin, people questioned say they have more confidence in the president than in congressional Republicans to handle the major issues facing the country. Obama held a much narrower 44% to 39% margin in March.

Remember all of those folks who said Obama was going to turn off voters with his economic populism? How Republican arguments about “class warfare” would generate doubts within the American mainstream?

Those predictions were wrong.

As for why the president’s approval rating is climbing, I suspect there are a few factors at play. The economy, for example, is improving, and a growing number of Americans are feeling more confident about the economic prospects. Obama’s messaging in recent months has also improved, as he shifts his energies into job creation and economic growth, as opposed to the debt-reduction efforts of the summer.

But let’s also not forget that many Americans have also spent the last few months getting a very good look at those Republicans who hope to replace the president next year. Does this make Obama look even better in the public’s eyes? I wouldn’t be surprised.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.