Arlen Specter's Primary Problem in Pennsylvania

Sestak also runs better than Specter in a general election match-up against Republican Pat Toomey.

Specter leads Sestak 46 percent to 42 percent, with 2 percent preferring someone else and 10 percent undecided. The margin of error is 5 points.

That differs from a Susquehanna Polling and Research survey released Wednesday that gave Specter a big lead over Sestak.

Among Democrats, Specter is viewed favorably by 68 percent and unfavorably by 30 percent, while Sestak is viewed favorably by 45 percent and unfavorably by 25 percent. But unlike Specter, who is so well-known that only 1 percent of respondents didn't have an opinion of him, 30 percent did not know enough about Sestak to say whether they regarded him favorably or not.

In general election match-ups Rasmussen released earlier, former Rep. Toomey, who was the challenger Specter switched parties to avoid, leads the incumbent 45 percent to 40 percent, with 6 percent wanting another choice and 9 percent undecided. The conservative Toomey had long been a thorn in Specter's side during his Republican days.

Sestak is in a statistical dead-heat with Toomey, leading him 38 percent to 37 percent, with 6 percent preferring some other candidate and 19 percent undecided.

The margin of error for the general election match-ups is 3 points.

Among the overall electorate, Specter is seen unfavorably by 52 percent and favorably by 46 percent. Toomey is seen favorably by 52 percent and unfavorably by 27 percent , with 21 percent not expressing an opinion. Sestak is regarded favorably by 37 percent and unfavorably by 34 percent, with 30 percent not sure about him.