The Pennsylvania Democratic primary may end up decided by the undecideds.

Senator Arlen Specter and Congressman Joe Sestak are vying for the Democratic vote in Tuesday’s primary, which will determine who  runs against the Republican candidate for the Pennsylvania Senate seat in November. SPORT BASEBALL

A Quinnipiac University poll released Monday shows the race is too close to call — with Sestak at 42 pecent versus Specter at 41 percent. Add to the mix 16 percent undecided and 25 percent saying they might change their mind, and the vote could go any which way.

“Sen. Arlen Specter has the party organization behind him, which should help with turnout. But Congressman Joe Sestak could benefit from the relatively large group of undecided voters.  Generally, incumbents don’t do all that well with undecideds, who are more likely to vote for the challenger or not vote,”  said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

“Moreover, as we have seen elsewhere this spring, there is an anti-incumbent mood in the electorate and Specter, with 30 years in the Senate, is the ultimate incumbent,” he said. The survey of 951 likely Democratic primary voters was conducted May 12-16 and has a margin of error of plus or minus 3.2 percentage points.

Others to watch on Tuesday:

Arkansas Senate Democratic primary, which pits incumbent Blanche Lincoln against Lt. Gov. Bill Halter. The most recent polls show Lincoln in the lead, but if the other candidate, D.C. Morrison, captures enough votes to prevent Lincoln from getting 50 percent,  that would force a June 8 rematch with Halter.