“It’s hard to analyze his plan because the specifics are so lacking,” said Robert L. Bixby, the executive director of the Concord Coalition, a nonpartisan group that advocates fiscal responsibility. Mr. Bixby praised Mr. Romney for setting spending goals and said his strategy of broadening the tax base is a good one. But he said Mr. Romney had presented less budget detail than other recent presidential candidates.

“You’re being promised a lot of pleasure without being told what the pain is,” Mr. Bixby said. “You have to be upfront with people and tell them what the trade-offs are.”