(CNBC) - Bob Corker has ruled himself out of consideration for Donald Trump's running mate, NBC News confirmed Wednesday.

The senator from Tennessee's withdrawal from the running was first reported by The Washington Post. Corker's Communications Director, Micah Johnson confirms to Channel 3 that the Washington Post article is accurate. 

Corker, 63, serves as chairman of the powerful Senate Foreign Relations Committee and was first elected to the Senate in 2006. He told Trump, the presumptive Republican presidential nominee, about his decision Tuesday, the Post reported.

"There are people far more suited for being a candidate for vice president and I think I'm far more suited for other types of things," Corker told the newspaper. 

Trump spent Tuesday with Corker, inviting the chair of the Senate Foreign Relations Committee to briefly join him onstage in Raleigh. The two men were a study in contrasts, as Corker stood at least a foot shorter than the billionaire businessman and spoke in slow, deliberate phrases instead of Trump's rapid-fire braggadocio.

"I wasn't going to say anything. I just came to visit," Corker began. "The rallies that I have back home aren't quite like this. Pretty cool."

He told the audience that he'd "had a pretty remarkable day" with Trump's adult children, employees and campaign staffers. "You know it says a lot about a - it says a lot about a person to meet their family, to spend time with their kids, if you will," he said, sharing some down-home advice with the crowd. "Somebody once told me it's not who you know in life, it's how you know them."

Chairman of the Hamilton County Republican Party said Corker would still be a strong candidate to serve in another role on Trump's administration.

"A cabinet-level position with Bob's banking and financial background, or whether it's as Secretary of State, none of those positions would surprise me at all," Tony Sanders said.

At least for the time being, Corker will remain Chairman of the Senate Foreign Relations Committee. A position with a lot of power.

"Going from being a Senator to a Vice President is actually a bit of a loss of autonomy, some loss of authority, some loss of control," said Dr. Michelle Deardorff.

UTC's Political Science Department Head speculates why Corker might have reconsidered, and said there are risks for any Vice Presidential nominee.

"He's going from the person who calls all the shots to the person who is responding to a president," Dr. Deardorff said.

New Jersey Gov. Chris Christie and Indiana Gov. Mike Pence are among those now considered possible vice presidential picks.

Separately on Wednesday, The New York Times reported that Sen. Joni Ernst of Iowa will have a prime-time speaking slot at the Republican National Convention later this month. The newspaper said the Trump campaign is also vetting her as a possible running mate.

Trump is slated to announce the convention speaker schedule Thursday.

The Associated Press contributed to this report.