The dam officially burst for Robert Menendez’s chances of political survival at around 11:16 a.m. Eastern time on Tuesday, when his New Jersey Senate colleague Cory Booker posted on X: "The details of the allegations against Senator Menendez are of such a nature that the faith and trust of New Jerseyans as well as those he must work with in order to be effective have been shaken to the core … I believe stepping down is best for those Senator Menendez has spent his life serving."

Until this point, Booker was practically the only holdout among New Jersey Democratic elected officials on the question of whether Menendez should resign. The indictment on operatic allegations of hundreds of thousands of dollars in gifts and bribes (including with gold bars) from an Egyptian businessman and his associates in exchange for various official actions is so over the top that even New Jersey’s less-than-scrupulous Democratic machine bosses have mostly ditched him. Booker himself actually testified as a character witness in Menendez’s first public corruption case, which ended in a mistrial. "It’s almost an understatement to say he was just a partner," Booker said in that trial, describing Menendez as a mentor and calling him "honest and trustworthy."

In short, if Menendez has lost Booker, he doesn’t have very many friends left in Democratic politics. Yet, against all odds, he still may survive this onslaught of pressure, especially if Democrats split the field against him in next June’s Senate primary. If Menendez digs in and gets multiple challengers, he could take enough of a sliver of the vote to prevail. As of now, only one challenger, Rep. Andy Kim of South Jersey, has jumped into the race. But many more are circling.

Booker is one of 18 Senate Democrats to ask for Menendez’s resignation, which would make the primary calculations a whole lot easier. Sen. John Fetterman (D-PA) was way out in front over the weekend, and on Monday Sens. Sherrod Brown (D-OH) and Peter Welch (D-VT) followed suit. But Tuesday was the real day of reckoning.

It started with Democratic incumbents in potentially tough re-election races next year: Jon Tester (D-MT), Jacky Rosen (D-NV), Tammy Baldwin (D-WI), Bob Casey (D-PA). It escalated with Elizabeth Warren (D-MA) and Martin Heinrich (D-NM). Numerous House members had joined the chorus, including most of the New Jersey delegation and former Speaker Nancy Pelosi (D-CA).

Then Booker made it safe for everyone else. As Demand Progress policy director Daniel Schuman noted, there’s now a "Booker line" among Senate Democrats: Anyone who called for Menendez’s resignation before Booker showed real leadership, and anyone afterward is piling on late. After Booker, Mark Kelly (D-AZ), Michael Bennet (D-CO), Amy Klobuchar (D-MN), Kirsten Gillibrand (D-NY), Mazie Hirono (D-HI), Ed Markey (D-MA), Raphael Warnock (D-GA), and Maggie Hassan (D-NH) were among those latecomers.

While Warren, Baldwin, and Booker are in leadership, those missing in action include Senate Majority Leader Chuck Schumer (D-NY) and Majority Whip Dick Durbin (D-IL). Given that Menendez has been adamant about fighting the charges and refusing to resign, Schumer and Durbin’s silence gives him just a tiny bit of cover. Schumer’s initial statement, stressing that Menendez is innocent until proven guilty and that everyone should let the process play out, most resembles that of Sen. Tom Cotton (R-AR), who is transparently stating that because he wants Democrats’ Menendez problem to fester. Either that or he’s just a consistent supporter of indicted federal officials.

There aren’t a lot of options for Democrats to deal with Menendez if he doesn’t comply. Per the Senate rules, expelling a senator requires a two-thirds vote, and as Cotton’s statement makes clear, Republicans are disinterested in helping Democrats out with their scandal. A vote that puts Republicans all on the same side as Menendez might have a short-term political benefit, but after that fades, the Democratic senator from New Jersey would still be standing trial for taking bribes.

The way to get Menendez out of the Senate that doesn’t rely on his assent is by voting him out. Kim, a former State Department official who won a contested House primary where he wasn’t the favorite in 2018, and then won two tough general elections (the seat was made a bit bluer for 2022), has affirmed that he’s seeing through a Senate run. But others are circling, including Tammy Murphy, the wife of New Jersey Gov. Phil Murphy. Reports indicate that she has been hearing out local and national political operatives about running for the seat.

If Menendez reverses course and resigns, you can expect a clown-car primary, with multiple candidates from the state’s political machines and factions. But if Menendez stays in, every other candidate besides Kim who enters the race makes it more likely that the indicted incumbent will survive. The only way Menendez can win a primary is with a split electorate, where he shaves off enough of his former base to eke through.

Presumably everyone in New Jersey politics knows this, which is why only Kim has jumped out. It’s hard for the various county machines to coordinate on a candidate when they each have their own favorite sons. Kim, who’s a bit outside the machine—he recently called for an end to the "county line" system, a way that county clerks can favor incumbents by putting challengers way down the ballot, away from the party line—didn’t have to take part in that process.

Menendez will fight the charges, and maybe even succeed, given how much the Supreme Court has limited the definition of corruption. Whether his days as a politician are numbered depends on the actions of a few key leaders in the Democratic Party.