As Hillary Rodham Clinton and Barack Obama prepared for their only televised debate before next Tuesday's vote in Pennsylvania, new polling data suggest there could be trouble ahead for the New York senator. Obama has opened up his biggest lead of the campaign in several surveys, while Clinton is suffering from record-high unfavorability ratings and the perception that sheis going negative.

In a new ABC News/Washington Post poll [PDF], 51 percent of Democrats say they would like to see Obama capture the Democratic nomination, compared with 41 percent for Clinton. This represents his largest lead of the primary season, according to ABC's analysis. Gallup's daily tracking numbers show the Illinois senator with about the same-sized lead.

Several factors seem to be at play in Obama's surge, but one important consideration is voters' belief that he is better equipped to win the general election. More than three in five Democrats in the ABC/Post survey cited Obama as the Democrat who will match up better against John McCain, while only 31 percent picked Clinton. That is a dramatic shift from February, when Clinton held a 5-point edge over Obama on this measure.

Clinton's favorability rating also hit an all-time low. A 54-percent majority now have an unfavorable opinion of her, the highest of any candidate and a 14-point jump since January. Obama and McCain have both seen their favorability ratings deteriorate over the last month, as well, but remain in the net-positive range, with McCain at 53 percent and Obama at 56 percent.

Contributing to Clinton's worsening reputation is the perception among Democrats that she is responsible for the increasingly negative tone of the primary contest. The number of Democrats characterizing the primary race as "mostly negative" has climbed 14 points since February to 41 percent and, of these respondents, 52 percent blame Clinton alone for the negativity, compared to just 14 percent who pointed to Obama. According to the survey's analysis, a 58-percent majority of all respondents also believe that Clinton is not honest or trustworthy.

Meanwhile, according to analysis, Obama's favorability numbers did not fall over the four days the survey was conducted -- last Thursday to Sunday -- as his comments regarding small-town voters received increasing attention in the media. Gallup found no change in Obama's overall lead over Clinton in the past several days.

New state polling [PDF] from the Los Angeles Times and Bloomberg also shows Obama gaining ground in upcoming contests. Clinton continues to lead Obama among Pennsylvania Democrats, 46 percent to 41 percent, but the Illinois senator is ahead of Clinton in Indiana and North Carolina, which hold primaries on May 6.

Still, the nomination battle looks far from over, and Democratic voters seems fine with that. Fifty-five percent of Democrats in the ABC/Post survey said that Clinton should stay in the race, even if she loses in Pennsylvania. And half also disagreed with the notion that the lengthy primary is hurting the party's chances in the general election, suggesting little urgency among Democratic voters to see the race resolved.