PHILADELPHIA — Pennsylvania voters who figure they've heard it all in the raucous U.S. Senate fight should brace for a final earful.

It's time for closing arguments as the tight race between Democrat Joe Sestak and Republican Pat Toomey heads into the final days, and they're bringing in the biggest names in the business to gin up voter excitement and help them win over the shrinking pool of undecided voters in this swing state.

Their showdown is among a handful of close contests that could be pivotal to Democratic chances of keeping control of the Senate.

Republican governors Tim Pawlenty of Minnesota, Chris Christie of New Jersey and Haley Barbour of Mississippi will flank Toomey at an event Friday. He will fly around the state Monday to chase last-minute votes with GOP gubernatorial candidate Tom Corbett.

He's also relying on several radio station interviews each day to help get his message out.

Sestak hopes to build strong turnout in heavily Democratic Philadelphia that could propel him to victory.

Democrats are making a final push to appeal to students and black voters who helped give President Barack Obama a double-digit win here in 2008.

Former President Bill Clinton is rallying college students in the Philadelphia area today. President Obama will swoop in Saturday for a voter canvass kickoff at Temple University in Philadelphia. Michelle Obama arrives Monday.

Sestak and Toomey are battling to succeed a fixture of Pennsylvania politics, five-term Sen. Arlen Specter, whom Sestak surprised in the May primary.

Voters can expect more din from a final burst of television attack ads. Outside groups on both sides are flooding the airwaves. The Democratic Senatorial Campaign Committee launched a new TV ad Wednesday accusing Toomey of favoring tax breaks that sent Pennsylvania jobs overseas.

With most polls showing a tight race, both candidates are well aware that the smallest of factors — a verbal gaffe, sluggish turnout in key counties or some other last-minute surprise — could decide one of the nation's marquee contests.

A Franklin & Marshall College poll released Wednesday showed about a fifth of voters were undecided.