And then something unexpected happened. Sen. Jeff Sessions, who had been uncommitted in the matter, came to the floor to announce that he will vote with Cruz and Lee. Back in July, when Lee circulated a letter asking his fellow senators to pledge not to support any spending measure that funded Obamacare, Sessions declined to sign. But now Sessions was on board, the first senator who hadn’t signed the letter to join the cause. “I intend to support you,” Sessions told Cruz, “and I’m not going to vote to move a bill where we are sure we’re going to be blocked from having any meaningful discussion of one of the most historic, damaging bills in maybe the last 100 years…”

Just a month ago, Sessions expressed deep doubts about the tactic. “I’m not sure it’s the best viable way at this point,” he said on Bill Bennett’s radio show in August. “I’ve looked at it really hard, I’ve talked to Mike, and I certainly respect what he’s doing, but I’m not convinced right now that this is going to be a way that will be successful and effective.” By Tuesday, Sessions had become convinced, even though he took care to express respect for colleagues who sided with leadership. “I didn’t sign the letter, and I’ve got some great friends who see it differently than I do,” Sessions said. “Good people, I think, can disagree on this.”

Sessions might not be alone. Speaking privately late Tuesday afternoon, a Republican senator suggested more lawmakers might soon join Cruz and Lee. They would not do so if it meant the filibuster would succeed and the government might shut down, but now that enough Republicans have made their positions known and shutdown is off the table, they will join the defund-by-filibuster effort. The reason, the GOP senator suggested, is that the outside groups pushing the defunding gambit — Heritage Action, Senate Conservatives Fund, FreedomWorks — are actively pressuring lawmakers to go along. Now that it’s a sure bet the continuing resolution will not be stopped, some Republicans might choose to seek safety from the groups’ wrath by joining Cruz and Lee. The perverse result could be that the Senate Republican caucus will appear more divided than it actually is.