Marco Rubio is adding another name to his growing list of Senate endorsements with the backing of Tennessee Sen. Lamar Alexander.
Alexander said Rubio would be a "strong and effective president" and touted the Florida senator as "the conservative candidate who can inspire us, win the election and lead our country."
"The stakes are high. If our nominee does not win, Hillary Clinton's justices will control the Supreme Court for 30 years and we'll be stuck with Obamacare forever," Alexander said.
"I have seen him take the lead in passing new laws to impose tough new sanctions on Hezbollah terrorists, and to get rid of incompetent managers who weren't doing their jobs to help veterans. He has proposed good new ideas for giving students more options for college," he said.
Alexander was a notable holdout even as a number of big Tennessee names lined up behind Rubio this week, including Gov. Bill Haslam and former senator Bill Frist.
Frist switched his endorsement from Jeb Bush just this week, and Haslam endorsed Rubio on Thursday. Sen. Bob Corker still has yet to endorse, and said this week he has no plans to do so.
Bush had deep ties to many of Tennessee's biggest Republicans — a number of members of his state team had worked in Haslam's administration, and he hired Alexander's former chief of staff to work in his administration.
Alexander also served in the George H. W. Bush administration, as Secretary of Education in the early 1990s.
Haslam and Alexander will appear with Rubio at a campaign stop in Knoxville, Tennessee, on Monday, a day before voters head to the polls to make their pick in Tennessee and a handful of other southern states in contests dubbed the "SEC primary."
Rubio has spent the past week barnstorming a number of the SEC states in hopes of gathering enough delegates — and perhaps notching a win or two — to give him a boost of momentum heading into the winner-take-all primaries on March 15.
Rubio is also hoping to eat into front-runner Donald Trump's support in some key states and prevent Trump from expanding his lead in the delegate count.
With its 58 delegates, Tennessee could be key to that effort. Rubio has made a handful of stops in the state before, most recently at a rally last weekend in Franklin, where he drew a crowd of more than 4,000 supporters.
This article originally appeared on NBCNews.com.