Cory Booker backs Menendez for reelection. Not that one.

Sen. Cory Booker is backing Rep. Rob Menendez in one of New Jersey's most competitive Democratic primaries, giving a notable boost of confidence to the son of the state's embattled senior senator.

"I've known Representative Rob Menendez for many years, and I'm not surprised he's been such an effective champion for the people of his district,” Booker said in a statement, first reported by the Hudson County View. “Rob has earned another term in Congress, and I'm proud to endorse his campaign for reelection so we can keep fighting together on the issues New Jerseyans care about most.”

Booker has been close with Rob’s father and New Jersey counterpart in the Senate, Bob Menendez, after serving with him in the upper chamber for over a decade. But he called on Menendez to resign last fall, after allegations of bribery and acting as a foreign agent emerged in a federal indictment. Menendez is set to begin his trial next week.

Now, the freshman Rob Menendez faces a tough reelection against Hoboken Mayor Ravi Bhalla in New Jersey’s 8th Congressional District, a Democratic stronghold mostly comprised of Hudson County, in North Jersey. Booker's endorsement is the latest in a long list of them for Menendez, including from local county parties. That would normally put a candidate in a comfortable position in a primary, but a federal judge earlier this year ordered primaries redesign ballots to do away with the so-called county line that gives party-backed candidates preferred ballot positioning and, as a result, much greater odds of winning.

Bhalla has centered his campaign on tearing down the county machine system and associating the younger Menendez to his father’s corruption allegations, although he is not accused of wrongdoing.

And on the Senate side, Bob Menendez is still deciding whether to run for another term, possibly as an independent since Rep. Andy Kim has all but claimed the Democratic nomination.

Booker did not say during a Thursday interview at the Capitol whether he would endorse Kim, but confirmed he would not be weighing in on the Democratic primary. In his run for Senate, Kim is also attempting to tear down the ballot design system that has reenforced New Jersey’s machine politics for decades. Booker said he thinks it's "a good thing" New Jersey is moving away from the party line on ballots.

“Newark, New Jersey, did not have partisan elections,” Booker, a former mayor of that city, said. “I don't think I would be here, frankly, because I challenged the machine, if you remember. I don't think I'd be here if we had partisan elections.”

Booker said he still works closely with Sen. Menendez. “I have an obligation to represent the state of New Jersey. There's two senators to our state, he has not stepped down.”

When Menendez stood trial in 2017 for a separate indictment, Booker testified as a character witness. Booker did not confirm whether he would testify again when asked at the Capitol this week.

“I'm proud that I spoke to Menendez I knew then,” Booker said. “One of the more difficult times I've had as a United States senator, was to call for a man to resign even though, as I said, I believe everyone has a right to be presumed innocent until proven guilty.”