At stake is control of the House, which most analysts believe will wind up in Republican hands before night's end. Republicans need 39 seats to take control.
Recent independent polls show that the South Jersey race is too close to call, but that Runyan had the momentum as of last week.
"This election has been about frustration," said Patrick Murray, polling director for Monmouth University. "We have a lot of frustrated voters looking for some way to voice that frustration. For many of them, they have the tea party, which has given voice to some of their concerns. Whereas, others are so frustrated, they won't vote."
Even with all the excitement the region's marquee race has generated, turnout is expected to be light, with less than half of the district's 460,000 registered voters expected to cast ballots.
"In some of these other races, you'll need a search warrant to find voters," said Democratic political consultant Pat Politano, who is not involved in the Third District race, which spans Ocean and Burlington Counties and includes Cherry Hill in Camden County.
Along with the state's 13 House seats, also on the ballot Tuesday are freeholder races in Gloucester, Burlington and Camden Counties, as well as a first-time partisan mayoral race in Evesham, and a special election for state Senate and Assembly in Camden County.
Polling places in New Jersey will be open from 6 a.m. to 8 p.m.
In Pennsylvania, voters are picking a replacement for U.S. Sen. Arlen Specter in a tough race between Republican former U.S. Rep. Pat Toomey and Democratic U.S. Rep. Joe Sestak. And they are choosing between Democrat Dan Onorato and Republican Tom Corbett to replace Gov. Rendell.