The latest New York Times and CBS poll came to the same conclusion that Rasmussen and others have reached — that Barack Obama failed to convince a majority of his sincerity in dumping Jeremiah Wright. Half of the 601 respondents believe that Obama acted out of political expediency and not conviction when denouncing Wright last week for his lunatic statements on HIV, al-Qaeda, and organic neural differences between white and black brains:

A majority of American voters say that the furor over the relationship between Senator Barack Obama and his former pastor has not affected their opinion of Mr. Obama, but a substantial number say that it could influence voters this fall should he be the Democratic presidential nominee, according to the latest New York Times/CBS News Poll. …

The poll, conducted after Mr. Obama held a news conference on Tuesday in which he renounced his former pastor, the Rev. Jeremiah A. Wright Jr., for making incendiary comments, found that most Americans said they approved of the way Mr. Obama had responded to the episode and considered his criticism of Mr. Wright appropriate.

But nearly half of the voters surveyed, and a substantial part of the Democrats, said Mr. Obama had acted mainly because he thought it would help him politically, rather than because he had serious disagreements with his former pastor. The broader effect of the controversy on Mr. Obama’s candidacy among Democratic primary voters was less clear in the poll, but enough of them expressed qualms about Mr. Obama’s relationship with Mr. Wright to suggest it could sway a relatively small but potentially important group of voters in the remaining primaries.

Forget the cross-party results. The sample is just as bad as it ever is with the NYT/CBS poll. The Times reports that Obama and Clinton enjoy strong leads against John McCain, but it’s easy to reach that conclusion when the sample includes twice as many Democrats as Republicans. The sample comprises 283 Democrats, 148 Republicans, and 170 registered independents. If Obama didn’t have a lead with that kind of sampling, the DNC could skip the period after the convention.

National polls mean nothing at the moment; the focus is Indiana and North Carolina. Unlike the last few contests, Tuesday’s races have pressure on both Democratic candidates to win states. Hillary Clinton has to win Indiana, where white, working-class voters comprise the vast majority of the Democratic Party. She has to show that she can keep winning in order to drown out the demands from other Democrats that she concede to Barack Obama.

For the first time in probably two months, Obama faces a make-or-break moment, this time in North Carolina. He has gone weeks without a victory, but even more problematic, he has simply performed poorly through a number of stumbles and gaffes. He looked tentative and vacillating in dealing with the outrageous comments made by Jeremiah Wright, while at the same time insulting Midwestern voters for supposedly clinging to guns, religion, and bigotry instead of big government.

North Carolina has a large base of African-American voters, and Obama was expected to beat Hillary by a wide margin, but his lead has all but disappeared. If he loses North Carolina, the party elders that will cast the deciding vote on his nomination may start believing that the rookie doesn’t have the talent yet to play in the big leagues. If he can’t win in North Carolina in a Democratic primary, where can he win in a general election contest?

If Obama wins a narrow victory in North Carolina, that may still be enough for Hillary to claim momentum. At some point, the Democratic superdelegates have to acknowledge that Obama may have been proven a liability for the general election. Their problem is that Hillary may not be any better.