Are the Republicans more vulnerable to the internal veto problem than the Democrats?

This is a follow-up to Monday's repost "The GOP needs the crazies more than the crazies need the GOP. " The whole piece is relevant, but in terms of this discussion, here's the money shot.

 Probably since 2008 and certainly since 2012, pretty much every nontrivial faction of the GOP has held veto power which means the question is no longer who has it, but who is willing to use it. The Tea Party was the first to realize this. Now the alt-right has caught on to the dynamic as well.

Andrew Gelman wasn't convinced:

I see your point, but given that the 2 parties have approximately equal support (OK, maybe the D's have 51% and the R's 49%, but it varies from election to election and they're both close to 50%), doesn't your argument apply to the Democrats as well? Indeed, wouldn't it apply to both parties most of the time for the past few decades? I agree there's something new in recent years with the crazies and the Republican party, but I can't see how it could be simple math. 

Let's see if I can shore up my claim.

                                            Sometimes 50 x 100% > 100 x 50%. Sometimes it's not.

Though I'm tempted to push back a little bit more, we can let the equal support stand for the sake of argument, but what exactly do we mean by the term? Are we talking about a hypothetical voter in an election where everyone participates or are we talking about actual voters who show up at the polls? And if so, which polls?

One of the great insights of the conservative movement was that most elected offices were undervalued. For instance, it was in many ways better to control the majority of state legislatures than it was to control the White House. Therefore, a substantial block of voters who will make it to the polls for every single election and reliably pick members of your party are especially valuable, valuable enough to justify losing a few other members to keep the loyal ones happy.

There are a lot of examples but the first that comes to mind is white evangelicals. 

From sociologist Lydia Bean:

Back in October 2014, pollster Robert Jones pointed out that white evangelicals were declining as a percentage of the U.S. population, even in the South – which could have been bad news for Republicans who count on loyal support from white evangelical voters. Starting in November 2014, Jones predicted, evangelical population decline could start tipping close races to Democrats in Bible Belt states like Arkansas, Georgia, Kentucky, and North Carolina. But Election Day on November 4th proved Jones wrong. White evangelicals turned out at high rates and played a major role in handing Republicans decisive victories in Senate races across the country. White evangelicals may be declining as a percentage of the population, but because they flock to the polls when Democratic constituencies often stay home, they still rule the midterms.

The group is shrinking (they now make up just under 15% of the population), but the reliability of their support has made them indispensable to the GOP, and recently they have come to realize the power they wield. They, along with other factions, have started demanding that the party make costly concessions. In its current incarnation, this dynamic started with the Tea Party.

By comparison, we haven't seen anything that like with the Democrats for a long time.  I think you'd have to go back before the Clinton administration to find examples of factions using the "I'll take ball and go home!" tactic to force the party into taking massively unpopular positions (at least not on the level we've seen on the other side). That doesn't mean there haven't attempts but none have gone anywhere.

One possible explanation is that the Democrats tend to rely more on the soft support of large groups (young people, non-white voters). These voters will be more likely to stay home if you take a toxic position and can fill in the hole with with higher turn-out if a fringe group bolts.