In his first national TV interview since committing the mother of all flip-flops to jump back into the race for the Senate, Marco Rubio went on Face the Nation yesterday to take a strong, bold stand against Donald Trump's signature policies — and to set the record straight that there was zero chance he'd be Trump's running mate.

"That's not for me a viable option," Rubio told host John Dickerson after being quizzed on the VP question. "The differences in policies that me and Donald have had are too big for something like that to work. It would be a distraction, quite frankly, to his campaign."

That's a pretty strong stand to take against his own party's nominee. But it's hard not to note that, in a pure coincidence, Rubio's tough anti-Trump talk came the same morning as new poll numbers showing Trump tanking in national surveys.

Indeed, the latest poll from the Washington Post finds Trump now trailing Hillary by double digits amid widespread disgust about his racist comments against the judge in a civil case against his for-profit college.

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Yes, Rubio has staked out a niche as an alternative to Trump dating back to the GOP primaries. But in the wake of his crushing Florida loss — as Trump was riding high in national and swing state polls — Rubio was largely silent except to say that he'd vote for the Donald for president.

Now that the public looks to be turning on Trump, Rubio isn't holding back. Here's what he told Face the Nation on Trump's plan to deport up to 11 million immigrants:

"The reality of it is, he can't do it. You can't round up and deport 11 million people," he told Dickerson. "There are people that need to be deported. Criminals need to be deported. But you can't round up and deport 11, 10, nine million people. The American people wouldn't stand for it once they saw what it would take to make that happen."

He also swiped hard at Trump over his ban on Muslims entering the United States:

"That's also not going to happen," Rubio said. "I think it's bad policy for the country to say you're going to have a religious exclusion."

These are good and correct takes. Well done, Marco!

But it's not just a cynic who looks at Rubio's suddenly robust anti-Trump speeches and the similarly declining national poll numbers for the GOP nominee and sees a prime political opportunist sensing his moment to jump back onto the national stage.

If Trump's rhetoric suddenly caught fire again nationally and — for whatever reason — the real estate magnate called up Rubio and asked him to be on his ticket, it would be very curious to see how Florida's junior senator might change his thinking.

