Sen. Marco Rubio, R-Fla., on Sunday ruled himself out as a possible vice presidential candidate, saying presumptive Republican nominee Donald Trump deserves a running mate who more fully embraces his positions.

On the Democratic side, Vermont Sen. Bernie Sanders declined to say whether he would be interested in the No. 2 spot if he cannot wrest the party’s nomination from former Secretary of State Hillary Clinton.

Rubio, in an hourlong interview on CNN’s “State of the Union,” said he expects to run for office in the future but may not seek re-election to the Senate (the deadline for a decision is June 24). He ruled out a run for Florida governor in two years.

Rubio admitted to making a series of errors during his primary run, which ended when Trump topped him in the Florida primary March 15.

Rubio said he would be a poor choice for Trump’s running mate because of the things the two said about each other during their primary contest, citing likely campaign ads that would be devastating, especially if they focused on the exchange the two had over the size of Trump’s “hands.”

Rubio said he would support Trump in November because the election of Democrat Clinton as president would be just “an extension of the past.” He even would be willing to speak on Trump’s behalf at the party’s Cleveland convention in July, characterizing Trump as “the ultimate change agent.”

Rubio said he would not advise Trump to change his campaign style since it’s been successful so far, but he disagreed with Trump’s strategy to bring up past Clinton scandals, saying he doesn’t like the direction. Trump has been hitting hard on Clinton’s use of a private email server during her tenure in the Obama administration and accused her of not fighting domestic abuse, calling former President Bill Clinton an abuser of women.

Sanders, who again pledged to stay in the primary race until the last votes are counted, dodged questions about whether Clinton needs a clean bill of health from the FBI over the email controversy but pledged to do whatever he can to “make sure Trump will not become president.”

On CBS’s “Face the Nation,” Sanders hit Trump for changing his mind repeatedly on whether he would agree to debate Sanders before the California primary June 7.

“The American people should be very concerned about someone who keeps changing his mind,” Sanders said.

Trump campaign adviser Paul Manafort said on ABC’s “This Week” the candidate is not afraid to debate Sanders.

The debate initially was proposed by comedian Jimmy Kimmel on his late night show Wednesday, and Trump took the bait — as long as $10 million to $15 million was donated to charity as a result. By Friday, however, Trump rejected the idea, saying it would be silly to debate the Democratic presidential candidate who came in second place.

Sanders, though hoping to go to the party’s Philadelphia convention in July with the majority of pledged delegates, said his pitch to superdelegates to get them to switch sides will rest on the need to select the strongest candidate to defeat Trump, insisting polls indicate that would be him.

There are about 700 superdelegates in the party who theoretically could decide the nomination, no matter how many pledged delegates are won by the candidates in the primaries and caucuses.

Fewer than 300 pledged delegates separate Clinton and Sanders, with a handful of primaries yet to go, including delegate-rich California. Among superdelegates, who can switch sides at will, Clinton leads Sanders 541 to 43. Sanders said he would talk to superdelegates in states where he outpolled Clinton to try to convince them to switch sides.