By Jon Cohen, Published: March 27 Half of all Americans now express unfavorable views of Mitt Romney, a new high for the GOP presidential hopeful in Washington Post-ABC News polling. The deteriorating public impressions of the former Massachusetts governor foreshadow a significant obstacle for him as he tries to shift the focus of his campaign toward a potential match-up against President Obama. Romneyâs negative numbers have jumped around this election cycle, but the overall pattern is similar to his trajectory four years ago: As he became better known, his unfavorables shot up far more rapidly than his positive numbers. Negative impressions are up eight percentage points in the past week, nudging past the previous high, which occurred about the time Romney suffered a big loss in the South Carolina primary. In the new poll, 50 percent of all adults and 52 percent of registered voters express unfavorable opinions of Romney, both higher â although marginally â than Obama has received in Post-ABC polling as far back as late 2006. However, the biggest difference between Romney and Obama is on the other side of the ledger: 53 percent of Americans hold favorable views of the president; for Romney, that number slides to 34 percent. Positive ratings of Obama steadily improved over the course of his fight for the 2008 Democratic presidential nomination â something not evident in Romneyâs ratings this time around, or last. Obamaâs relative low point among independents in 2008 was in mid-April, when 57 percent said they had favorable impressions and 37 percent had unfavorable ones. In the new poll, Romney is underwater with independents: 35 percent view him favorably, 52 percent unfavorably. Independents are more evenly divided on the president â 50 percent favorable, 46 percent unfavorable, about where theyâve been in recent polls.