Mississippi Governor Haley Barbour (Bruce Newman/AP)

“Look, if this election is about Barack Obama’s policies and the results of those policies, Barack Obama’s gonna lose,” Barbour told reporters. “Any other issue that gets injected into the campaign is not good for the Republicans. Republicans should want this election to be what American presidential elections have always been — a referendum on the incumbent’s record. Barack Obama cannot win a second term running on his record. Zero chance. So anybody that talks about anything else is off-subject.”

Barbour’s comments came after reporters asked him whether he would advise Texas Gov. Rick Perry to stop talking about so-called “birther” conspiracies. Perry, a GOP presidential candidate, said in two recent interviews that he was not sure whether Obama was born in the United States despite the president’s release of his long-form birth certificate showing he was born in Honolulu. In an interview this week with John Harwood of The New York Times and CNBC, Perry said: “It’s a good issue to keep alive.”

Barbour was in Washington, where he held a press briefing about the congressional super committee and offered suggestions for cutting spending, as well as reforming the tax code and entitlement programs.

Barbour, who seriously considered a presidential bid of his own before deciding this spring not to run, said he would not endorse a presidential candidate. But Barbour, who is a leader of the GOP-leaning political action committee American Crossroads, said he plans to be “actively involved” in the general election.

“Almost all of ’em are friends of mine,” Barbour said of the candidates. “I like ’em.”

“I think a lot of donors, just like a lot of precinct men and women and a lot of grass-roots activists, want to wait until they feel comfortable that they’ve identified the Republican candidate with the best chance of winning in November 2012,” Barbour added.

Asked for his reaction to the economic plan Perry unveiled Tuesday — which includes an optional flat income tax, personal accounts for Social Security and major government spending cuts — Barbour offered some praise but cautioned that he had not seen the details of Perry’s plan.

“Is a flat tax good policy? Yes,” he said. “It’s not the only good tax policy, but it certainly can be very good tax policy, particularly if you eliminate a lot of deductions.”

“In terms of Social Security reform, I can make the argument for private accounts,” Barbour added. “Clearly, if you look at places like Singapore, Australia, where they have required savings — that’s their form of Social Security, that you’re required to save so much of whatever you’re earning and the government takes it and invests it so you can’t spend it — this is not something that’s not done in the world.”