Sen. Joe Manchin (D-WV), who is not seeking re-election to another term in the Senate, has been testing the waters over the past several months about a possible independent or third-party presidential run as a moderate centrist alternative to President Joe Biden and former President Donald Trump.

During an event in Cleveland, Ohio, on Thursday, Manchin suggested that, if he were to launch a presidential campaign, fellow moderate and retiring Sen. Mitt Romney (R-UT) would be his top choice as a running mate, Breitbart reported.

Likely due to Ohio being the location of the event, Manchin also mentioned former Sen. Rob Portman (R-OH) as being under consideration to run alongside him in a theoretical campaign for the White House.

Manchin mentions Romney, Portman as possible running mates

According to Fox News, Sen. Manchin addressed a small gathering of around 150 attendees at a breakfast forum at the City Club of Cleveland as part of his nationwide "listening tour" to gauge the level of support there may be among American voters for a moderate centrist presidential run.

Asked repeatedly by the moderator, City Club CEO Dan Moulthrop, about a potential presidential bid, Manchin initially replied, "Guys, listen, I’m not running for anything. I’m basically running to try to get people involved."

That said, if he were to run, the senator said, "Hypothetically, if I was picking my running mate … really, who I would ask right now is Mitt Romney."

Manchin added, "Maybe Rob Portman would be right there, too. Rob is a dear friend of mine. What a good man, what a good man."

Run would likely be on No Labels "unity ticket"

For the past several months, per Fox News, Sen. Manchin has teased the possibility of an independent or third-party run as an alternative to the two presumptive major party nominees, Democratic President Biden and Republican former President Trump, most likely as part of a so-called "unity ticket" put forward by the politically centrist No Labels organization.

That group aims to provide a home for the "politically homeless" voters who are turned off by the ideological extremes on the left and right and would like to see more moderate options for the presidency.

Manchin could also possibly draw support for an independent or third-party run from a 501(c)(4) political nonprofit organization known as Americans Together, which was launched last summer by his daughter, Heather Bresch, and is run by a couple of the senator's close associates in West Virginia, according to The Intercept.

However, per Bresch, the nonprofit is separate from and unaffiliated with her father, but that could easily change in the future if Manchin launches a presidential campaign.

Romney says "No" to Manchin's proposal

According to Utah's Deseret News, Sen. Manchin may want to go ahead and search for other potential running mates if he mounts a bid for the presidency as Sen. Romney, who previously fell short with his own failed White House bids in 2008 and 2012, signaled that he has little desire to launch a third run.

When asked about what Manchin had said, Romney jokingly replied, "Well, that’s really presumptuous. I would be the president. He would be my running mate."

He added more seriously, "No, I’m not going to run for president. Certainly, I’m not running for vice president. But (Manchin is) kind to say that. We’re good friends."