As has been the case throughout the past year, Barack Obama maintains a sizeable favorability advantage over Mitt Romney. Currently, 55% of registered voters express a favorable opinion of Obama, just 45% say the same of his challenger.

Voter impressions of Romney have improved substantially over the past six months. In March — during the heat of the GOP primary campaign — his favorability rating fell as low as 29%, when many Republicans who backed other candidates for the nomination did not feel favorably toward him. Much of the recovery in his ratings since this period comes from within his own partisan base. Currently, 88% of Republicans offer a favorable impression of Romney, up from 76% in July and just 60% in March.

Romney’s image also has become more positive among independents since the spring, though it is little changed since July. Currently, as many independent voters view Romney unfavorably (47%) as favorably (46%). In July, independent voters also were divided (41% favorable, 44% unfavorable). In March, just 28% of independents viewed Romney favorably; 52% had an unfavorable impression.

Obama’s standing among independents has improved significantly over the past few months. Currently, 50% of independents offer a favorable impression of Obama, up from 41% in July and 43% in June.

A review of Pew Research Center and Gallup favorability ratings from September finds that Romney is the only presidential candidate over the past seven election cycles to be viewed more unfavorably than favorably.

Related: See an analysis by Andrew Kohut in the New York Times. Read More

Russell Heimlich  is a former web developer at Pew Research Center.