I'd say the GOP's leaders have a lot to do with this by actively courting more extreme elements of American society and then whipping them up in frenzied hatred and bunker mentalities to win elections, but not really realizing how this would create a more extreme voter base that would elect increasingly conservative politicians, who would then continue the cycle.
Nixon, Reagan, and GHW Bush were more than happy to fear-monger on the campaign trail when it helped turn the base out, but once elected were happy to sit down with Democrats to govern (horrible thing that is, isn't it). Just look at how different the GHWB of the 1988 and 1992 campaign rhetoric was from his actual Presidency; worlds apart.
However, all those Baby Boomers who grew up in the tranquil 1950s, turbulent 1960s, depressing 1970s, and "prosperous" 1980s were helping power these Presidents by turning out to vote for them in these elections, and ate up all the crap that was fed to them and believed it.
Then, in the 1990s, generation changed happens all across government, with the Republican Revolution of 1994 the most famous case. The New Deal generation's influence in government dies off as they literally die off themselves, and are replaced by these "new conservative" Baby Boomers who lionize Reagan and his "revolution".
Then 9/11 happens and the Muslims become their enemy. Increasing numbers of people realize that gays aren't actually horrible, and support for their rights ticks up. So what does GW Bush do in 2004? Campaigns on his war on Islamic terror and banning gay marriage, cementing the image in the long run among young voters and immigrants that the GOP is a party of hateful white Christians.
Then Obama gets elected, and the once-revolutionary Baby Boomer generation is painted as "RINOS" by a new generation of Baby Boomers (many born in the last half of the Baby Boomer generation) and now the first half of the Generation X group) even more extreme who get elected in 2010.
And now we approach 2016, and those 2010 Tea Partiers are suddenly "not conservative enough".
It's a positive-feedback loop of extremism. The leaders of the GOP, both past and present, have a lot of blame to cast upon themselves for 1.) inviting these people into their party, and 2.) feeding their paranoia and resentment for electoral gain.
"Lay in the bed you made" and all
Brilliant.
