A frequent spot holder on Forbes’s list of the world’s wealthiest individuals, Buffett endorsed President Obama in 2008, but has not historically been an overly political figure – until now. In August, he penned an op-ed in the New York Times asking policymakers to raise taxes on millionaires and billionaires like himself. He has claimed he pays a lower tax rate than his secretary, thanks to a tax structure that favors those whose income comes from investments.

“My friends and I have been coddled long enough by a billionaire-friendly Congress,” Buffett wrote. “It’s time for our government to get serious about shared sacrifice.”

With Obama struggling to persuade Republicans to accept a tax hike on the wealthy to pay for the deficit reductions that the GOP has demanded, Buffett has become a veritable stump speech line for Obama; he calls the tax hike the “Buffett Rule,” and mentions the billionaire now with the frequency that Republicans mention Reagan.

“All I’m saying is that those who have done the best in this country should contribute to its success,” Obama said Thursday during a jobs speech in Cincinnati, Ohio. “All I’m saying is that Warren Buffett’s secretary shouldn’t be paying a higher tax rate than Warren Buffett.”

But now, some Republicans are mentioning Buffett with the frequency they used to mention Soros, the financier and philanthropist whose ardent support for left-wing causes and politicians made him Enemy No. 1 for Republicans for much of the last decade. Former Fox News host Glenn Beck called him a “puppet-master” for instigating world chaos and insinuated that Soros, who was born in Hungary, had collaborated with Nazis.

Now that Obama has seized Buffett as an emblem of big business supporting tax increases, Republicans are demanding that Buffett release his tax forms for public scrutiny. Rep. Dave Camp (R-Mich.) said, “Frankly, Mr. Buffett needs to give his secretary a raise,” and freshman Rep. Tim Huelskamp (R-Kan.) said Buffett had bitten off more than he could chew and was afraid to show proof.

“Conservatives tend to level ad hominem attacks against their ideological or policy opponents rather than deal squarely with the arguments that those opponents present,” said Michael Vachon, a spokesman for Soros. “To that extent, there is some similarity” between him and Buffett, he said.

Soros donated tens of millions of dollars to campaigns targeting President George W. Bush, but was less active on the political scene during the 2010 cycle and in the first months of the current cycle.

Yet Buffett may be a more difficult target for Republicans than Soros, because while Soros has seemed to relish being a partisan figure, Buffett’s role has been more limited to advocating for a particular economic policy, said Kyle Kondik, a political analyst at the Center for Politics at the University of Virginia.

“I think it’s going to be a lot harder,” he said. “Warren Buffett is a pretty respected guy in American life, whereas George Soros is a foreigner, and a person who has bankrolled sort of lefty causes for a long time.”

But there’s at least some evidence that wading into the fray of one of Obama’s signature policies can drag down even a political outsider.

Take entertainer Andy Griffith, who 56 percent of voters in his home state of North Carolina viewed positively in 2008 when asked by the Democratic firm Public Policy Polling, also based in North Carolina.

Then Griffith cut television ads in 2010 supporting Obama’s health care initiative, and his favorability fell to 44 percent by last September.

The former star of The Andy Griffith Show is down to 32 percent as of last week, and his unfavorable ratings have more than doubled since 2008, jumping from 9 percent to 23 percent.