So says PEW, echoing NBC:
...the Wright controversy does not appear to have undermined support for Obama's candidacy. The latest nationwide survey by the Pew Research Center for the People & the Press, conducted March 19-22 among 1,503 adults, finds that Obama maintains a 49% to 39% advantage over Hillary Clinton for the Democratic nomination, which is virtually unchanged from than the 49% to 40% lead he held among Democrats in late February. Obama and Clinton continue to enjoy slight advantages over John McCain in general election matchups among all registered voters.
The new polling suggests that the Wright affair has not hurt Obama's standing, in part because his response to the controversy has been viewed positively by voters who favor him over Clinton. Obama's handling of the Wright controversy also won a favorable response from a substantial proportion of Clinton supporters and even from a third of Republican voters.