What I'm about to say isn't really original and may even be fairly obvious, but it just struck me this morning for some reason.
The Republican Party quite simply has a more authoritarian party culture than the Democratic Party does. This isn't meant as a value judgment--plenty of countries with internally authoritarian party cultures have stronger and better-functioning multiparty democracies than the United States. It's also not meant as some sort of backhanded way of claiming that the Republicans "are authoritarians" or advocate more "statist" policies (whatever that means). I don't even mean to repeat the old "Democrats fall in love, Republicans fall in line" saw--while that may have been true in the past, that dynamic clearly reversed this year. What I mean is simply that, once Republicans do have a candidate, and especially when they have a president, they start to treat him in a more caudillo-ish way than Democrats do their candidates and presidents.
We saw this especially clearly at the conventions last summer. Both primaries had gotten pretty negative by the end, but the Republican primary started out negative, was negative for way longer, and involved far more personal attacks on the losing contenders by the eventual nominee (and vice versa, to be fair). And yet Bernie Sanders was booed at the DNC for endorsing Clinton, and Ted Cruz was booed at the RNC for not (yet) endorsing Trump. We've seen it even more clearly since November, with the formerly staunch anti-Trumpist Jeb Bush doing a whole song and dance on Twitter about what a bold conservative leader Andrew Puzder is, even though Jeb is clearly smart enough and may even have good enough intentions to know that Puzder is the Mustapha Mond of fast food CEOs. And now John McCain has said he'll vote to confirm Rex Tillerson, even though Tillerson's connections and attitudes go against everything McCain believes on foreign policy.
So we shouldn't expect to see much resistance to Trump's policies from the McCains or Rubios of the Republican Party. Even though there's at least as much ideological daylight between them as there was between Obama and Bart Stupak or Ben Nelson in 2009, they're likely not to be nearly as dedicated moderating forces on any of Trump's policies as Stupak and Nelson were on Obamacare. This isn't because the Republicans are less ideologically diverse than the Democrats, or even because individual Republican politicians have less courage of their convictions necessarily, but because Republican Party culture morally values deference to leadership in a way that Democratic Party culture simply does not.
It really comes down to this... If we're in the center, then the far right extreme part of Republicans is Fascism, the extreme part of Democrats is Communism. Both suck. Let's be frank. I think the country as a whole is really Center-Left. Economically we're centrist because you don't want to the system up, our gold-mine is money, but socially we're left, because we don't care if you want to marry the person of same-sex or go through with abortion but we want you educated on that decision. I personally believe we'll be a 3 party system in the future. We'll have the Extreme Right, the Centrist and the Extreme Left. Centrist just want to keep it moving, we'll be like the Labour Party (but without Tony Blair) in England. Just keep the budget balanced, that's all we want.