The more I think about it, the more plausible it’s beginning to sound.

Bernie Sanders well might become Hillary Clinton’s running mate against Donald J. Trump.

I had been thinking all along that Clinton might look more toward someone with, say, a Hispanic background. Former San Antonio Mayor Julian Castro — who’s now housing secretary in the Obama administration — was a logical choice.

Sen. Elizabeth Warren’s name has popped up. That’s an interesting pick, too. An all-woman Democratic ticket? You go, girls!

But now it seems quite possible that Sen. Sanders — who’s been battle-tested and proven to be up to the fight — might be the right kind of No. 2 to challenge Trump and whomever he selects as his running mate.

Sanders already has pulled Clinton to the left on some of his pet issues: income inequality, war in the Middle East to name just two.

At one level, he’s already won the ideological fight within the Democratic Party. Indeed, if he’s not chosen, I truly can hear Sanders making a “the dream shall never die” speech at the Democratic convention, echoing the stirring address given by vanquished Sen. Ted Kennedy at the 1980 convention that re-nominated President Carter.

However, if Clinton picks Sanders as her VP nominee, then he’ll continue the fight forward.

One obvious drawback is his age. He’s 74. He’d be 79 at the end of a first Clinton term. There might be a commitment to serve just one term as vice president if a President Clinton were to seek re-election in 2020.

Of course, only the candidate knows who she’s going to pick.

As for Trump, he said he’s narrowed his list to “five or six” individuals. He vows to pick an actual Republican and someone with “political experience.” He, too, has a list of former rivals he might consider, although at least two of them — Sen. Ted Cruz and Gov. John Kasich — have all but told Trump to jump in the proverbial lake before asking either of them to run with him.

The mystery of who’ll be running for president in the fall has just about been solved.

Now we’ll await these important choices for the No. 2 spots.

I’m starting to “feel the Bern.”