California the heartland of liberalism, and its demographics give 55 Electoral College votes to the Democratic party candidate for president to start their campaigns with.
This is 15 more votes to the 9 mid-west "safe" Republican states or 16 more than 7 safe deep south GOP states. Add the 161 other safe Democratic states in New England,upper Midwest and the Pacific Northwest and Dem's start with 216 of the required 270 Electoral College votes.
California,where the Democratic Party holds all elective offices statewide and control both chambers of the legislature will not be competitive for the GOP on the state legislature, governorship and senatorial level, much less the congressional (currently 39 Dem's to 14 GOP) and presidential level for generations.
The substantial Hispanic (33%-71% Dem) and (7%) Black (7%-93 Dem) populations will give Democrats an unshakable hold on the state until a substantial middle class evolves among those demographics.
It's quite simple, If Donald Trump loses to Hillary Clinton in November the Republican Party as constituted will never capture the presidency ever again. No Republican of any stripe, a conservative, in his day, McCain (or Cruz if you prefer) centrist Romney, populist Trump could or can ever win the state.
If it holds together, which would be by no means certain, it or it's successors will, from time to time, control either of both houses of Congress and a majority of Governorships and other elected offices.
If Hillary wins then the current GOP will be in a worse position that the Democratic Party was from 1860 to 1932 when it had only two presidents elected in 72 years. This was partly because of reconstruction, when a number of states did not participate, and also because of internal divisions and general economic prosperity.
If Trump loses and Hillary enacts the immigration program as described by "NeverTrumper" renegade (Palin describes such as "traitors") Noah C Rothman in a 'Commentary' article, then it will be impossible for a Republican to be elected president via the Electoral College;
The simple fact is, because of the head start California gives to the Democratic candidate, that no Republican nominee can win in the Electoral College without Florida's 29 votes. A quick analysis of the map at 270toWin where viewers can assign states to the candidates shows that even if Trump won Ohio/Pennsylvania/Colorado Hillary would only need Nevada or Virginia. The New York Times Nate Cohn sets this out in some detail.
However, even if by some magic Trump managed to squeak out a win without Florida this would only delay things by one election. With so many illegals enrolled to vote and with a good ground game the Texas Democratic Party would commence to turn that state purple then red. With the loss of 55 California, 38 Texas, and 29 Florida electoral votes the presidential campaigns, such as they would be, would be over before they started.
It is a strong possibility that if a Trump defeat was assisted by the machinations and negativity of the "NeverTrump" spoilers, then the Hillary enabled demographic changes would just be an adjunct to the end of a Republican presidency as the party could well split after November.
If the "NeverTrump" faction believe that by helping to defeat Trump they, the Jeb/Graham/Romney/Ryan/Cruz-ite dead-enders/Kristol/Levin/Deace/ et al think they will inherit a GOP like the 2012 grouping they are utterly mistaken. It is, frankly, impossible to conceive that the Trump/Palin supporters would even contemplate aligning themselves to such a concept.
The only check on a rampant leftist presidency stretching into the future would be, as happened from 1860 to 1932 an occasional opposition controlled Congress (even if that were, for convenience sake, a coalition of former Republicans). The Supreme Court, subsequently a permanent leftist structure, would
make America an unrecognizable social polity.
For Trump supporters, for "NeverTrump" diehards for the disengaged Cruz and other ex-candidates supporters the choice is absolutely clear and stark. Vote for Trump and give whatever GOP faction you support a voice in future presidencies and the Supreme Court or enable a Hillary presidency and the end of the Republican Party holding the presidency ever again.
If the Republican establishment allied to the "Never Trump" recalcitrant ultra-conservatives make a Trump loss worse than it might have been a break-up of the GOP
may well ensue further consolidating a Dem hold on the presidency for the foreseeable future,