In the days leading up to the Feb. 1 Iowa Caucus, the Republican presidential field has undergone some significant shifts. After last Thursday’s debate, the consensus seemed to favor a three-man race — Donald Trump, Ted Cruz and Marco Rubio. But some would go even further to say it’s really down to Trump and Cruz. Establishment versus Outsider. But who is who?

As for the rest of the field, Rubio’s path to the nomination seems to be getting more, not less, difficult. His battles with Cruz and Chris Christie have exposed the problems his record poses for both conservatives and the rest of the base, particularly on immigration. And without a win in the early states, as seems likely, many wonder if Rubio can stay strong long enough to turn the tide.

And what of establishment darling Jeb Bush? Well, Jeb! has spent much of this contest polling in the single digits, and despite (or rather because of) his attacks on Trump and his numerous and uninspiring policy speeches, he just isn’t gaining traction with an electorate looking to throw the bums out. An almost sure loss in New Hampshire could mark the end for Bush.

As for Carly Fiorina, John Kasich, Rand Paul and the rest? We can expect to see them all picked off in the early primaries as their predictably meager showings lead to a bleeding of cash and supporters and the inevitable campaign suspension announcements.

How did it come down to Trump vs. Cruz? And what about the framing of Establishment versus Outsider? Trump has never held elective office, so he is perceived as an outsider. But he has long been a backer of Democrat politicians and has held a number of progressive views (New York values, one might say) that don’t match the conservative base of the party. So does that make him Establishment?

Cruz is a senator in Washington, so by comparison to Trump, is he Establishment? Hardly, considering that Cruz has made his name by tweaking the nose of the GOP establishment (including calling Senate Majority Leader Mitch McConnell a liar on the Senate floor) and generally taking on what he calls the “Washington cartel.” He is arguably the most resolutely conservative of all the Republican candidates, and his voting record and his public stance on the issues bears that out.

Take Cruz’s stance against ethanol subsidies. He refused to pander to Iowa power brokers, while other candidates dutifully bowed to King Corn and the mandates and subsidies that undermine the free market and exceed the government’s constitutional role. Trump on Tuesday called for increasing the ethanol blended into gasoline.

If there are any other questions as to whether Cruz is indeed the outsider candidate, just take a look at Iowa Republican Governor Terry Branstad’s words on the subject: “Because as Iowans learn about his anti-renewable fuel stand, and that it will cost us jobs, and will further reduce farm income, I think people will realize that it’s not in our interest. I don’t think that Ted Cruz is the right one for Iowans to support in the caucus.”

Traditionally, Iowa governors, regardless of party affiliation, have steered clear of offering opinions of the caucus. But Branstad’s son runs a group that’s part of the ethanol lobby, so he couldn’t remain silent.

The establishment’s rejection of Cruz is due to his solid conservatism and his combativeness with his fellow Republicans in Washington. In fact, there are reports that the establishment is beginning to coalesce around Trump — not because he represents the establishment GOP, but because he is the leading Not-Cruz. The establishment would rather have a dealmaker who boasts of having bought politicians and, more importantly, a moderate-to-liberal candidate, than a principled conservative.

Republican donors and consultants now don’t seem so quick to write off a Trump nomination. Is it because his momentum now makes him more viable than originally perceived? Is it because of the staunch support of his base? Yes, on both counts.

Trump’s supporters are an important asset that cannot be underestimated if Republicans want to win the White House this year. They are motivated because they are fed up with the establishment in Washington. But if that is truly the case, then who would better serve those voters’ interests: Trump or Cruz?

Sarah Palin chose Trump, endorsing him Tuesday. The former vice presidential candidate has been a standard-bearer for the Tea Party movement since she emerged on the national stage in 2008, so her endorsement of Trump is important.

At first glance, it’s also a puzzling move, though it shouldn’t be. On April 15, 2009, a big day in the early life of the Tea Party, Trump said, “I don’t march with the Tea Party.” He also said Obama “really has made a great impact on people,” and, “I think he’s doing a really good job.”

But Palin says, “Enough is enough. These issues that Donald Trump talks about had to be debated. And he brought them to the forefront. And that’s why we are where we are today. … We are mad and we’ve been had.”

Given Palin’s supposed conservative bona fides, she should have endorsed Cruz, particularly when one takes into account Trump’s previous progressive stances on some issues. And Cruz rightly credits Palin with helping secure his Senate seat. Yet Palin went with The Donald, signifying that she has been more populist than conservative from the beginning. Nevertheless, perception is everything, and her endorsement will only help Trump and hurt Cruz, especially in Iowa.

Republicans are highly motivated to win the White House this year. After eight years of Obama, and a potential four years of Hillary Clinton, the GOP needs to be prepared to do whatever it takes to win. However, the party needs to guard against leaving the bedrock principles of conservatism to be trumped by nationalistic populism. Otherwise a White House win will be a pyrrhic victory.