Mitt Romney
A new ad from an Obama-backing super PAC claims the money Big Oil has made from high gas prices has gone toward supporting Mitt Romney's presidential campaign. REUTERS

Even as Mitt Romney inches steadily towards securing the Republican presidential nomination, his standing in the eyes of American voters continues to slip.

A new Washington Post/ABC News Poll found that fully half of Americans said they have an unfavorable impression of Romney, a former Massachusetts governor, compared to 34 percent of voters who said they viewed Romney favorably.

That is the highest unfavorability rating for Romney yet recorded in a Washington Post/ABC poll, and seems to confirm that perceptions of Romney are deteriorating as the nominating contest drags on -- a Washington Post/ABC poll conducted in February found that voters said by a 2-to-1 margin that they liked Romney less the more they learned about him.

While Romney has opened a substantial lead in pledged delegates for the Republican national convention, exit polls have indicated that voters choose Romney out of pragmatism more than idealism. Romney consistently captures a majority of voters who say defeating President Obama is their priority, whereas voters who say they most value a candidate who is a true conservative or has strong moral character have tended to choose Romney's Republican rivals.

Polls generally predict a tight race in a hypothetical general election matchup between Obama and Romney. But the latest Washington Post/ABC news poll underscores a wide favorability gap between the two men: more voters viewed Obama favorably than unfavorably, by a 53-43 margin.