Marco Rubio on his "worrisome" endorsement of Donald Trump

WASHINGTON (CBS News) - After endorsing the Republican presumptive presidential nominee Donald Trump, Sen. Marco Rubio, R-Florida, has continued to cast doubts over his party's nominee. During a sit-down interview for Face the Nation, host John Dickerson asked the former Republican presidential candidate what he found worrisome about Trump.

"He [Trump] still hasn't defined himself." Rubio said from his hometown Miami, Florida but also said, "I think he's in the process of doing that."

Rubio referenced Trump's speech last Wednesday, criticizing the Democratic presumptive nominee Hillary Clinton's past and record in the State Department, as positives for the Trump campaign.

"Donald is not running against George Washington or Abraham Lincoln here. He's running against Hillary Clinton." The Florida senator said. "Someone who has incredible ethical issues that need to be examined. Someone whose time at the Department of State needs to be carefully looked at for its failures both in foreign policy, in Benghazi, and in other circumstances that she needs to be held responsible for."

Rubio also stated that everywhere the Clintons go, "Scandal and drama seems to follow, at a time when this country can't afford it."

During the interview, Dickerson asked Rubio if his party had any regrets about nominating the controversial business man to head their ticket.

"In this campaign season, the issues that underpin the conservative movement were not necessarily what was determining the outcome of this election." Rubio said and added, "You had a lot of voices who claim to be or are from the conservative movement who decided to overlook all sort of ideological or policy differences in order to get on behind an attitudinal approach to politics."

Rubio stated that he disagreed with that approach and said the result of this has divided the party.

"If you see how the conservative movement's been divided, you have leading conservatives in our party and in our movement that are now looking for ways to affect the outcome at the convention even now."

The Florida senator acknowledged that this was the reasoning behind his senate reelection bid saying that there are "other things we should be working together on."

"We have three branches of government here. And one of them is the legislative branch and in particular the Senate that acts as a check and balance on the presidency no matter who wins." Rubio said and added, "I want to make sure that we have people in the Senate that will act as a check and balance on the president no matter who's elected."

For more of our interview with Sen. Marco Rubio click here.