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. Romney’s 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...