WASHINGTON ― Back in mid-January, while Democrats were still recovering from the shock of the presidential election, 13 Democrats cast a dead-of-night vote that in previous years would have gone largely unnoticed.

It was against an amendment from Sen. Bernie Sanders (I-Vt.) that directed a Senate committee to write legislation allowing for the re-importation of cheaper prescription drugs from Canada. Perhaps the most prominent of the baker’s dozen was Sen. Cory Booker (D-N.J.), who just the day before had given controversial and impassioned testimony against Attorney General-nominee Jeff Sessions, at the time a fellow senator from Alabama.

The backlash caught Booker and his colleagues by surprise, and in many ways it presaged the furious energy that would soon be unleashed by progressives against both Trump and elected Democrats unwilling to stand up to him. It was a sign that things had changed in Washington and that standard operating Democratic procedure would no longer be acceptable.

The memo has been received. On Tuesday, Booker will join with Sanders at a press conference on Capitol Hill to announce his support for a drug re-importation bill.

From a policy angle, Booker has previously been open to the idea of re-importing drugs from Canada and even voted that same night for a measure aimed at lowering drug costs. But politically, activists have long considered him to be a reliable ally of Big Pharma, which is a dominant industry in New Jersey. Thus, his break with the industry at a public event with Sanders is meaningful politically. If the goal of the resistance has been to stiffen the spines of Democrats, it’s working.

Of course, there is no policy without politics. If and when Democrats gain control of government, they’ll be under tremendous pressure from their base to follow through on their promise and do something about soaring drug costs.

The drug industry is powerful in Pennsylvania, too, and Sen. Bob Casey (D-Pa.) joined Booker on that late-night vote in January. Since then, resistance in Pennsylvania has been fierce, with activists gathering every Tuesday to pressure lawmakers to oppose the Republican corporate agenda. Casey has not been immune and he faces re-election in 2018 in a state that Trump won with an upset victory. He, too, will join Booker and Sanders on Tuesday in announcing his backing of the bill.

Booker and Casey said they were able to add robust safety provisions to the measure, which won over their support.

The bill is co-sponsored by Reps. Elijah Cummings (D-Md.) and Lloyd Doggett (D-Texas), as well as Sens. Martin Heinrich (D-N.M.) and Angus King (I-Maine).

Watch the full press conference below:

CORRECTION: Texas Rep. Lloyd Doggett is a Democrat, not a Republican.