Republican presidential front-runner Mitt Romney issued a bruising broadside attack Wednesday on President Obama’s credibility, saying he is running a stealth campaign to deceive American voters and challenging the nation’s news editors to be serious referees in this year’s election.

“I find myself missing the presence of editors to exercise quality control. I miss the days of two or more sources to a story, when at least one source was actually named,” Mr. Romney said, addressing the annual convention of the American Society of News Editors in Washington.

The challenge to the press and the newly emboldened attacks on Mr. Obama come a day after Mr. Romney swept primaries in Wisconsin, Maryland and the District of Columbia and appeared to have put himself on firm footing as he pushes to wrap up the Republican presidential nomination.

Mr.