New Jersey incumbents don't lose primaries. Nearly impossible to get around the county line especially in the cost-prohibitive NY and Philly media markets.
The county line will help Menendez, but it makes the biggest difference in lower offices. Menendez won't lose because his opponent is exceptional, he would lose because the voters know he's corrupt. The voters that would take down Menendez would come to ballot box to vote against him, not to vote for his opponent. If someone is against Menendez, they can just vote for a candidate in a different column. Especially when the Senate race is at the top and isn't just a lower office in a column of lower offices.
I think the most likely Senator, if not Menendez himself, is his son. Bob will not retire and leave an open primary unless it's a foregone conclusion his son will be Senator. He wouldn't back down from a primary from Murphy, Oliver, Sherrill, or any of his possible opponents.
That being said, I really think Sherrill or Kim could beat him. His joke opponent got 37% in 2018. Sherrill has a lot of money left over from her congressional campaigns and would be bankrolled by Bloomberg. Gottheimer is influential in the House and is too unlikeable himself to be an insurgent candidate, while the other House Dems are too senior to run for Senate.
