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If that’s truly the case, the jukebox has been belting out hits in recent days.

Senate Majority Leader Harry Reid, Nevada Democrat, as well as senior White House adviser David M. Axelrod and the president’s economic guru, Austan Goolsbee, have singled him out for his optimistic read of the tax compromise. Sens. Charles E. Schumer of New York, Barbara Boxer of California and Carl Levin of Michigan also have argued that Mr. Zandi’s research showed that extending unemployment benefits delivers a bigger bang for the buck than the Republican push to extend tax cuts to individuals who make more than $200,000 per year.

“If you care about getting the economy going, you are going to be for increasing unemployment benefits quicker than tax breaks for millionaires,” Mr. Schumer said last week. “[Unemployment insurance] benefits are 400 percent more stimulative than tax breaks for the wealthy, according to Mr. Zandi.”

Republicans, including Sen. Charles E. Grassley of Iowa and Rep. Jeb Hensarling of Texas, have countered by feeding Democrats a spoonful of their own medicine.

“What I find interesting is how many Democrats have come to the floor to quote the economist Dr. Mark Zandi,” Mr. Hensarling said last week on the House floor. “He is probably the most quoted economist by the Democrats. Yet he, himself, has rejected the idea of raising taxes in this economy.”

Others seemed to be for Mr. Zandi before they were against him.

Last week, Sen. Tom Harkin also held up Mr. Zandi’s analysis as proof that unemployment benefits should be extended. But days later, after Mr. Zandi praised Mr. Obama’s tax deal with Republicans, the Iowa Democrat was ready to swear off the entire economic profession.

“We are in a whole brave new world now,” the Iowa Democrat said. “I don’t think any of these economists really know what is going on.”