Mark Cuban has been one of the Harris campaign’s most visible outside surrogates in recent months.

Now he’s making it official.

The billionaire businessman will embark on a series of formal campaign appearances for Kamala Harris beginning with stops alongside the vice president later today, a campaign aide told Yahoo Finance exclusively.

It’s a move that comes as the Harris campaign amps up its efforts to reach young men and further capitalize on the "Shark Tank" star's popularity in the worlds of both finance and sports.

The first stop will be alongside the vice president today in Milwaukee and La Crosse, Wis.

Then, the former majority owner of the Dallas Mavericks (he still has a minority share in the NBA team) will headline a town hall in Phoenix, Ariz., Saturday. He will also make a Sunday stop in Grand Rapids, Mich., alongside second gentleman Douglas Emhoff.

The crisscrossing of the country from Cuban comes as Donald Trump’s own billionaire backers are increasing their prominence for this stretch of the campaign, with the end of voting now less than 20 days away.

Tesla (TSLA) CEO Elon Musk is currently in Pennsylvania for a "series of conversations" with voters on behalf of Trump, and campaign finance filings on Tuesday also revealed that Musk donated just under $75 million to his Trump-supporting super-PAC last quarter.

Cuban’s role as Harris’s voice to business

The coming move from the Harris campaign is an escalation of Cuban’s prominence on Harris's behalf but far from the first contact between him and the campaign.

He has appeared on an array of podcasts and national media in recent months to tout his support for her, and he’s also repeatedly critiqued Trump for issues like trade and taxes.

Cuban has also become a prominent pro-Harris voice on X, formerly Twitter, where he's often engaged with Musk who owns the platform.

He also joined a call with reporters in September on behalf of the campaign, where he talked about how he held regular conversations with aides and, at the end of the process, "I get back a serious well-studied response; that's the antithesis of what Donald Trump is doing."

"He doesn't think these things through," he added of Trump, calling some of his ideas "often ridiculous if not insane."

Cuban also often discusses healthcare in his defenses of Harris after launching the Mark Cuban Cost Plus Drug Company in 2022 aimed a lowering generic drug prices.

The new role for Cuban also comes as the Harris-Walz campaign increases its ad spending on male-dominated platforms — including during major sporting events and on video game websites.