Over the past several weeks, a quarter of New Jersey's congressional delegation announced plans to step down from office.

New Jersey Legislature (Tim Larsen, Governor's Office)

In the 1st Congressional District, Rob Andrews has already resigned to take a job in a law firm; in the 3rd District, Rep. Jon Runyan said he will not seek re-election; and 12th District Congressman Rush Holt made the same announcement earlier this week.

Most political experts expect the incumbents to be replaced by members of their own party when elections take place later this year.

"Because of the redistricting that occurred in 2010 and 2011, New Jersey's congressional districts tend to be gerrymandered in terms of one political party typically dominating over the other," said Brigid Harrison, professor of political science at Montclair State University.

She pointed out the 12th District used to be fairly competitive, but now because of redistricting, it is dominated by Democrats. And in the 1st District, state Sen. Donald Norcross (D-Audubon) is a shoo-in.

"I don't think that Congressman Andrews' seat had a chance to get cold before Mr. Norcross scooched in and occupied it," Harrison said.

Harrison added that there is a chance a Democrat could capture the 3rd District seat -- where Republican Jon Runyan is leaving -- but it's too soon to tell.

"The thing about New Jersey politics, though, is that you could always have a celebrity candidate," Harrison said. "A well-known candidate could walk in and say, you know what? I'd like to serve in Congress right now."

Harrison also thinks Andrews, Holt and Runyan made unconventional moves by choosing to vacate their seats.

"What is surprising is that these three individuals decided to give up what was really safe and secure, seats that all of them could have held for the next two decades at least," Harrison said.