Orlando (CNN) Sen. Marco Rubio still won't take back the many attacks he launched at former rival Donald Trump when they faced off in the bitter presidential primary. But ahead of voting in Tuesday's Senate primary in Florida, the freshman lawmaker is reluctant to alienate Trump's supporters in a state the billionaire won by nearly 20 points.

"The primary is over," Rubio told CNN in an interview Monday following a campaign appearance with veterans in Fort Myers. "Republican voters chose a nominee and we have a choice between two people ... I do disagree with Donald on a number of things. I disagree with Hillary [Clinton] on everything."

The balance Rubio is trying to strike is about more than Rubio's political career. His success in November could be crucial to helping the GOP maintain its tenuous grip on the Senate.

In a sign of how far he's moved, Rubio said he was open to campaigning with Trump in Florida if schedules allow. In campaign appearances, Rubio tells voters that the country "can't afford" to elect Clinton. And despite his repeated denunciations of the businessman's negative and personal tone on the trail, he refused to take Trump to task for recently calling Clinton a bigot.

"Democrats have been calling Republicans bigots for a long time," Rubio said. "I think Hillary Clinton has a lot or problems. I think she's corrupt, she's dishonest, she lies constantly. She's always in the center of some controversy."

Pressed on the caustic characterization, Rubio said Trump would have to account for his own words.

"I do think some of the policies she stands for do harm minority communities, absolutely," Rubio said. "I can tell you, I don't want Hillary Clinton to be president."

After he ended his presidential run, GOP officials -- who were increasingly worried they were on track to lose the Senate to Democrats -- successfully lobbied Rubio to reverse his pledge to quit the chamber. But even as he runs for another term, Rubio refused to commit to complete a new six-year term, a clear sign a presidential run in 2020 remains an option for the ambitious young politician.

"No one can make that commitment because you know now what the future is going to hold in your life personally or politically," he said. "I can commit to you this, if I'm running to a be a US senator, I'm prepared to let the US Senate be the last political office that I ever hold."

Rubio is part of a group of more than a half dozen Senate Republicans whose fate this November is in part linked to Trump's. Republicans need the controversial candidate to stay competitive with Clinton to boost their chances of keeping control of Congress. They also need to court Trump's passionate supporters as well as disillusioned establishment Republicans and independents who may be turned off by the GOP nominee.

Polls show Clinton with an edge in Florida and Rubio with a lead over his likely Democratic opponent, Rep. Patrick Murphy, who has come under scrutiny for claims about his professional qualifications as a certified public accountant and claims of being a small business owner.

"He is a hyper-partisan liberal and Florida cannot afford a hyper-partisan liberal in the United States Senate," Rubio said about Murphy teeing up his general election argument against his foe. "Unlike Patrick Murphy, I don't make up my qualifications."

Murphy denied he has made any false statements and said Rubio was making the charge to draw attention away from his dismal attendance record in the Senate when he was running for president.

"He doesn't like the job and this is what he is going to do to distract from the facts," Murphy told CNN. "I have been a CPA since 2009 and if elected to the US Senate I would be the second CPA in the history our country to serve there. If you asked me, our fiscal house could use some private sector experience."

In the interview, Murphy said "yes, I do," when asked if he trusts Clinton, even though polls show most Floridians distrust the former secretary of state. And he said he was "as shocked as a lot f people I spoke with" about Rubio's support for Trump.

"Donald Trump is perhaps the most racist bigot ever to make it this far," Murphy said.

Yet, Rubio is also taking heat from the right for not embracing Trump tightly enough. Carlos Beruff, the wealthy businessman who spent millions of his own cash in Tuesday's primary, said that voters are "irritated" by Rubio's handling of Trump.

"I will vote for him, but I'm not going to endorse him," Beruff said. "Because I don't respect the guy."

Unlike many of his Senate colleagues, Rubio is in a more awkward position with his own party's nominee after their many toxic encounters on the campaign trail that included the senator saying Trump would be a "disaster for America" and was a "con artist" who could not be trusted with the nuclear codes.

Reminded that he had charged Trump was too erratic to be trusted with the nuclear codes, Rubio repeated, "the primary is over."

Asked how he could support Trump despite his contention that the GOP nominee wouldn't keep the country safe, Rubio deflected and put the focus back on Murphy.

"How can Patrick Murphy support Hillary Clinton after all the outrageous things that keep coming out about her?" he said.

Rubio is trying to make the case to voters that he's been an "effective" senator, yet the Florida lawmaker has been repeatedly attacked for skipping Senate business while running for president. In the interview, Rubio would not say if he regretted the large number of votes and hearings he skipped, saying it's common for senators to miss the chamber's business when seeking the White House.

"I don't know anyone who's ever run for president as a senator who didn't," Rubio said. "Hillary Clinton missed more than I did."

On Wednesday, Trump is slated to give a major speech on immigration; but in a sign of how Rubio is navigating his party's nominee, he pulled his punches when asked about Trump's hardline views and rhetoric on the subject, which contrasts with the senator's approach on the issue.

While he said that deporting millions of undocumented immigrants is not the "right approach" and that Mexico is "not going to pay" for a border wall to be built, as Trump contends, Rubio refused to say if he thought Trump should soften his rhetoric on the issue.

"I'd be more focused on the Democrats rhetoric on this issue, which is to accuse any Republican who doesn't agree with their version of immigration reform as being anti-immigrant," he said. "That's ridiculous."