Let’s start with an easy one: What does a Republican believe?

Well, maybe not so easy. In the Reagan and Bush eras, there was a rather simple answer for what the GOP wanted: a hawkish foreign policy, limited government, and social conservatism -- the various factions all living under one Big Tent.

But by 2012, the year Rick Santorum and Ron Paul both commanded large subsections of the Republican base, it was becoming increasingly hazy what the GOP stood for, and how it could translate that message into something electable at the national level.

It turned out a guy with no political experience – one who had spent much of his life as a liberalish New York Democrat – had the answer to that riddle. Donald Trump, guided by his strategist Steve Bannon, figured out how to cobble together a winning message with a hodgepodge of ideological parts.

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Trump’s formula was inelegant, and remains so. But from a vote-getting standpoint, it also worked.

But even as the party’s base has become increasingly unpredictable and non-doctrinaire in its opinions, the Republican governing class has become in recent years more rigid. With the retirement of John Boehner, Paul Ryan became not only the party’s chief ideologist but its political leader in Washington.

Washington Republicans, with their tax-cutting zeal and love of open markets, always saw the GOP base as an extension of themselves. This is the major reason that they never thought Trump could win the primary, let alone the general.

And it was the hope of Ryan’s fellow ideologues that Congressional Republicans would essentially run the government, at least from a domestic policy standpoint, once the GOP retook the White House. As the conservative power broker Grover Norquist said in 2012, the job of the next Republican president would be “to sign the legislation that has already been prepared.”

The legislation is indeed ready to sign. But when Norquist made that comment, it’s unlikely he was imagining Trump would be the guy with the pen.

How much of the GOP agenda is Trump really willing to expend political capital on? He must know he wasn’t voted in to enact Medicare reform, an idea without a constituency that is nonetheless near to Ryan’s heart and central to his thinking.

Trump also promised not to let people die on the street during his presidency. How will he square that with an Obamacare repeal that puts an industry-friendly scheme in its place?

Or what about industrial policy, this practice of the government intervening to help manufacturing-sector workers, which Trump has fully embraced in practice before even taking office? Does anyone think Trump will stop attempting to keep manufacturing jobs here, even though doing so flies in the face of free-market orthodoxy his party embraces?

Deals can be hardened out of small-ball disagreements. But we are talking about major, fundamental disagreements. There is a looming Republican schism and it’s about more than Trump’s lack of philosophical mooring. It is about two very different visions of what the GOP should be.

Ryan rose in the Republican ranks by being an attractive, articulate ideologue in a party that was supposed to be all about ideology. The Trump-Bannon formulation of how the GOP should work, however, is not really ideological at all. It’s about getting better results for certain economic and demographic groups, presumably at the expense of others.

Like most ideologies, modern conservatism insists that it contains the best set of policies for everyone: rich and poor, white and black, and so on. It’s difficult to know how many people actually believe all that, but it’s been the central message of the GOP for decades.

Bannon, meanwhile, has a habit of describing politics as a zero-sum game between competing groups, namely working- and middle-class Americans versus an ascendant elite class. And the populism Bannon talks about is, in a sense, neither left nor right, and instead all about serving the interests of the downwardly-mobile.

“Trump is a builder,” as Bannon said to Bloomberg’s Joshua Green this fall. “And what he’s built is the underlying apparatus for a political movement that’s going to propel us to victory on Nov. 8 and dominate Republican politics after that.”

And this movement, Bannon has made clear, is not about enacting the Ryan agenda. It’s about displacing Ryanism, and the whole modern conservative project, with populism and economic nationalism.

“The conservatives are going to go crazy,” is how Bannon put it to Michael Wolff after the election. “I’m the guy pushing a trillion-dollar infrastructure plan. With negative interest rates throughout the world, it’s the greatest opportunity to rebuild everything. Shipyards, ironworks, get them all jacked up. We’re just going to throw it up against the wall and see if it sticks.”

So what does a Republican believe? It’s hard to say. There is now a Party of Trump and a Party of Ryan. The former rejects ideological rigidity in favor of policies it sees as beneficial to Middle Americans. The latter is ideological in the extreme, the end result of decades of conservative movement insistence that the path to victory was paved by intellectual seriousness and a deluge of policy white papers.

In the short term, there are ways for these two camps to live together peacefully within the GOP. There will be alliances of convenience between them, particularly when it comes to overturning President Obama’s agenda and lowering taxes.

But eventually the two sides will go to war, and one will come to dominate Republican politics after that. And that’s because the disagreements are simply too profound to allow for any other outcome.

Trump’s and Bannon’s vision is diametrically opposed to Ryan’s, and at some point both sides will run out of compromises they’re willing to make. The Big Tent simply won’t be big enough for all of them.