As Ben Carson gets reassigned from the Veep selection team to helping prepare for the Trump Ryan Summit on Thursday (or TRST), it seems the selection process for vice presidential running mate is proving a little trickier than Donald Trump had perhaps expected. Nikki Haley, Rick Scott, and Rob Portman all pleaded or pledged call of duty to their local electorates in South Carolina, Florida, and Ohio. The governors of South Carolina and Florida, and the senator from Ohio all said they love their current jobs and will be working hard to serve their constituents. And get re-elected.

And then there’s Marco. Who will not be a senator by late January next year. Unlike Ted Cruz.

Marco Rubio laid down a sort of a marker these past few days, pledging to help down-ticket Republicans keep their seats in November. And clearly stating he’s not interested in being Trump’s running mate. In other words, he’ll atone for his ambitious rush at the presidency by going into the trenches and helping his party hold onto a majority in the Senate. A tough proposition. And the House. A little easier, hopefully.

He’s doing it as an act of contrite humility and gratitude to the party that has made him a known political commodity across America. Right? Maybe. Maybe it’s also his way of building a base for 2020. He was often accused of being a no-show senator. So now he can free himself of the upper chamber and re-build his grass roots following. Right?

There may be a problem there. He will have no office to leverage into media coverage. He won’t be a candidate. He won’t have much money until he is. And there’s something more. In a fascinating piece in Atlantic, Molly Ball suggested that Trump has set off an earthquake underneath the civil war that’s been raging in the GOP for a few years now. Conservatives blame Establishment Republicans for Trump – all talk and no action and no promises delivered. And all that frustration leads to Trump.

While establishment Republicans blame conservatives – angry rhetoric aimed at the party’s institutions that inflames the base and allows demagoguery to flourish – first Ted Cruz calls his chamber’s leader a liar. Then Trump, who has notched the angry rhetoric up another level. But he’s basically paving the footpath that Ted Cruz blazed. Devoid of the conservative platform that motivated(s) the Texas Senator.

So here comes Trump who, Ball suggests, has unified parts of each side of the civil war in the GOP. As she writes:

He redrew the old battle lines, combining the passionate anger of the grassroots and the win-at-all-costs pragmatism of the elites … Trump smashed the old categories and asked a new set of questions …

In other words, Cruz on the one side, and Jeb and Marco on the other, no longer knew that the battle they were fighting had changed. And if Molly Ball is onto something, then the problem facing Marco Rubio is not deciding whether he’s conservative or establishment, but rather what side of the new civil war, Trump vs. the GOP-as-we-know-it, he’s on. And defending conservative principles – as he has been doing – is no longer enough.

Does Marco join the Trump Train and try to make a deal that saves something of the convervative platform? And possibly his electoral chances in 2020, although that’s dangerous to predict? Or does he try to fight Trump’s corporate takeover of a divided GOP? And from what platform? The Libertarian Party? Nope. Host his own show on Talk Radio? The money could be good, if he’s any good at radio. Blog?

Rubio has clearly chosen to oppose the Trump Train. But he risks being left behind, handing out pamphlets to late arrivals at the station.