Meanwhile, former Republican U.S. Senate Majority Leader Bill Frist has endorsed Rubio as well as Tennessee's GOP establishment begins mobilizing on behalf of Rubio to promote his effort to become the top alternative to Republican frontrunner Donald Trump in Tuesday's Super Tuesday primaries and caucuses in a dozen states.
But a note to the Team Rubio campaign, which is spending $4,000 on the ad in the Chattanooga market: You may need to step up your game.
That's because GOP rival, U.S. Sen. Ted Cruz of Texas, and a Cruz-allied "super PAC" linked to a wealthy Fort Worth money manager are spending nearly ten times as much as the Rubio campaign in the Chattanooga market alone.
Cruz's campaign has purchased over $14,204 in air time for ads while the Stand for Trust super PAC is spending another $24,000 for a combined $38,204, according to Federal Communications Commission filings examined by the Times Free Press.
A Texas firebrand, Cruz has pitched himself over the course of the campaign as an anti-establishment, Christian conservative and Tea Party adherent best able to represent the party in November.
But both Cruz and Rubio have run smack dab into the Trump phenomenon.
Trump so far is spending nothing in the Chattanooga market which also reaches into Northwest Georgia and portions of Alabama, both Super Tuesday states.
Cruz, meanwhile, plans to hit Nashville hard on Friday where he has a combination rally/on-stage "interview" with popular Fox News opinion show host Sean Hannity.
Later in the day, Cruz will go to Opryland Hotel to speak at the National Religious Broadcasters' annual convention.
Some Tennessee political operatives, meanwhile, are scratching their heads over the fact that neither the Rubio nor the Cruz campaign took advantage of Tennessee early voting where an estimated 250,000 people voted in the GOP primary through the 10-day voting period that ended Tuesday.
Two operatives said they think that figure may account for as much as a third of the GOP's total vote. Cruz did manage to get his Chattanooga ads up on the last day of early voting.
Earlier Thursday, Haslam, who just last week told Tennessee reporters he's not sure people don't pay that much attention to prominent officials' political endorsements, endorsed Rubio.
"To win in November, conservatives need a candidate who inspires Americans from all backgrounds," Haslam said in a statement released by the Rubio campaign. "With Marco standing next to Hillary Clinton on a debate stage, the choice between the future and the past will be clear to every American."
Haslam said Rubio, a U.S. senator from Florida, "has the innovative policy agenda to reclaim the American Dream for all our people, and his conservative ideas will bring the Republican Party – and America – into the future."
Just last week, Haslam was coy about an endorsement and even raised considerable doubts about whether the average person even cares about them.
"I really don't know," the governor said. "As I said to other folks, I don't think people pay all that much attention to who the governor endorses, just like who newspapers endorse and a lot of other things in today's world."
While acknowledging such endorsements can make a splash, Haslam went on to say "how many voters that actually impacts, I guess we'll see. As a candidate I'd always rather have elected people's endorsement thatn not. But again, I'm not certain at the end of the day how much that impacts."
In the Rubio ad which begins airing Friday in Chattanooga, Haslam says "To win this November, conservatives need a leader who can unite our party and inspire our country. That's why I'm endorsing Marco Rubio for president.
"I'm Bill Haslam. Marco will take power from Washington and send it back to states like our founders intended, because we know best how to grow high-quality jobs. And Marco has the conservative vision and history to reclaim the America Dream. I hope you'll join me and vote for Marco Rubio. You'll be proud you did."
Frist, meanwhile, said that Rubio "understands that it takes more than angry rhetoric to be an effective candidate for president. If the Republican party wants to win back the White House, we need a candidate like Marco Rubio that can appeal to all types of voters."
Cruz campaign officials did not immediately respond to a request for a copy of their ad.
Politico, meanwhile, reported earlier Thursday that the Stand for Truth group purchased just over $1 million in television commercial time in Tennessee, Georgia, Arkansas and Oklahoma.
According to Politico, the spot begins with clips of Clinton, Donald Trump, and Bernie Sanders, warning that "with so much at stake, we can't afford to take a chance on this election."
The ad also highlights pro-Cruz themes such as his evangelical background and takes a swat at Rubio over immigration policy, Politico reported.