Sen. Mike Lee (R-UT) endorsed Sen. Ted Cruz (R-TX) as his choice to become the next president of the United States Thursday afternoon.

Lee appeared at a campaign rally with Cruz in Cora Gables, Florida. Lee said that Cruz is “unstoppable,” hinted that other senators will soon endorse him, and called on Marco Rubio to drop out of the presidential race.

Utah @SenMikeLee says he would tell @marcorubio that it's time to unite behind @tedcruz. — Jason Whitely (@JasonWhitely) March 10, 2016

The Utah Senator is well-regarded as one of the brightest voices for constitutional conservatism in the Senate. He and Cruz have maintained a strong friendship since arriving on Capitol Hill. The two have fought together for a pro-Liberty, pro-Constitution agenda in Washington.

Sen. Lee had previously been on the campaign trail with both Cruz and Sen. Marco Rubio (R-FL).

Lee will officially endorse Cruz at an event on Thursday afternoon in Florida, according to reports.

The endorsement comes just five days before several major Republican primary contests on March 15.

The Cruz campaign sent out an advisory that he will be making a major statement at 3:00 PM EST at the University of Miami.