Maryland Gov. Martin O’Malley (D) mocked Republican presidential nominee Mitt Romney for not offering more specifics about his tax plans during a spirited performance on “Fox News Sunday.”

Gov. Martin O'Malley (D) outside the State House in Annapolis recently. (Photo by Aaron C. Davis/The Washington Post)

“I’m glad you practiced some lines for this,” Fox News Sunday host Chris Wallace told O’Malley, who debated Sen. Kelly Ayotte (R-N.H.) during the show’s first segment Sunday.

O’Malley, the chairman of the Democratic Governors Association, has become a regular on the national talk show circuit, but Sunday marked his first appearance on the Fox show.

At one point, Wallace accused O’Malley of mischaracterizing Romney’s tax plans by talking only about the part of the proposal that cuts tax rates, which some economists have said would cost $5 trillion over a decade.

Wallace pointed out that Romney also has said he would make his plan “revenue neutral” by eliminating various tax loopholes and deductions.

“He won’t say which loopholes and deductions,” O’Malley said, a point on which Wallace agreed.

Ayotte said that Romney has made clear that his plan would not result in upper-income Americans paying less or middle-income Americans paying more.

“What he has said is he’s going to work across the aisle” to develop specifics, Ayotte said.

O’Malley and Ayotte also tangled over the state of the economy and Obama’s stewardship of it.

Wallace noted that even with the announced drop this week in the unemployment rate to 7.8 percent, no president since Franklin Delano Roosevelt has been re-elected with such a high figure.

“No president since FDR was left bigger job losses, bigger unemployment, bigger deficits, more wars, than President Obama was by the failed policies of George W. Bush,” O’Malley countered.

Ayotte argued that the drop in the unemployment rate was not very impressive, given many of the new jobs were part-time work.

“You can’t support a family on part-time work,” she said. “I don’t think there’s any cause to celebrate here.”