Runyan's seat is tough for Dems without Cherry Hill. LoBiondo is likely safe if he runs again, but Dems would likely be favored in an open seat race in the 2nd, which is a much stronger Democratic heritage than the 3rd, which has almost none.
LoBiondo's seat has trended more Democratic, but it wasn't always that way. It was the seat that was once held by the conservative Republican Rep. Charles Sandman (R-NJ). Sandman was elected in 1970 and in 1973 he successfully challenged incumbent 1st term Gov. William Cahill in the GOP primary. He won, but in the general election, he was absolutely creamed by Democrat Brendan Byrne. Then, in 1974, Democrat William Hughes, a somewhat conservative Democrat who ran a close race against Sandman in 1970, beat Sandman convincingly in the Watergate year. At the time Hughes retired it was assumed that the seat would switch parties, and it did, as LoBiondo won. Hughes was a guy who won repeatedly, despite the GOP carrying his district in Presidential contests.