Obama lengthens lead

WASHINGTON — Barack Obama has taken clear leads over Hillary Rodham Clinton among white men, middle-income earners and liberals, allowing him to catch his faltering rival in their race for the Democratic presidential nomination, a national poll showed Monday.

The Associated Press-Ipsos survey highlights how the bottom is falling out among some supporters of Clinton, the New York senator, since the last survey was taken two weeks ago. Since that poll, Obama has gained momentum by winning 11 consecutive primaries and caucuses while taking a small lead among delegates to the party's convention this summer.

The Illinois senator leads Clinton by 23 percentage points among white men and by 17 points among liberals — groups that were evenly divided between the two in early February. He has a similar advantage among people earning $50,000 to $100,000 annually — whom she led earlier by 13 points.

Clinton maintains robust leads among some groups that have been cornerstones of her candidacy, including those age 65 and up, white women and people earning under $50,000 annually.

Overall, Obama has 46 percent to Clinton's 43 percent, a virtual tie. Clinton had a slight 5 point lead nationally in early February.

Obama's advances among voting groups are even more stark when viewed longer term.

In mid-January — when primaries and caucuses were just beginning — Clinton had a 7-point lead among all men, a group she now trails by 25 points. The two were about even among college graduates, whom Obama now leads by 20 points.

A majority of Democrats in the poll also said elected officials and party leaders who may play a pivotal role in choosing the candidate should back the one who leads in the primaries and caucuses. As of now, that would be Obama.

These so-called "superdelegates" may be crucial because neither Obama nor Clinton may accumulate the delegates needed to ensure the nomination at the August convention in Denver. Allowed to support whomever they like, these officials have been under enormous pressure from both campaigns.

In the AP-Ipsos poll, 57 percent said these officials should support the contender ahead in the voting while 38 percent said they should back whoever they think gives Democrats the best chance of winning the White House. Of those saying the officials should follow the voters, two-thirds said they should heed nationwide results while a third preferred basing it on the officials' own districts.