What percentage of overall GOP voters constitutes "the base" you are describing?
Because whenever i hear these calls for a third party, i wonder how a group of voters who aren't even numerous enough to win a plurality in the GOP primary (which itself is only 30-35%% of the electorate at best) can manage to win a general election.
It doesn't matter, now, does it.
First we were told the GOP doesn't need us anyway.
Second, this isn't about anything but principle this time around. I understand that some people will have problems with that concept, but we aren't voting for the liberal candidates.
There are a number of deal breaking issue stances or traits which prohibit that, as a matter of conscience.
Third, if that party is to grow, if not now, when? If not us, who?
Continuing with the GOP isn't going to get us the government we want, that being one based on the United States Constitution, as amended, as close to original intent as can be, with power and rights restored to the States and the People where that power and those Rights belong.
Obviously, the Democrat Party will offer no relief.
You ask us to define a number we cannot. You want a percentage answer to a question which has not been asked. Insufficient data. The electorate has been handed Hobson's choice and will reflect that. The question which will be answered at the polls will be which candidate they fear most, not what they prefer.
There are those who might side with us who fear the boogeyman of Clinton enough to vote for Trump. That is on their conscience. If they aren't happy with that, they can still work to build a third party, however they vote this time.
For those who view burning the village to save it as a nonviable option, there is the opportunity to develop and build another option for the future. If too few are willing to take that route, so be it, we will have tried, and the Republic will decay into a criminal cartel/oliarchy, as it has been doing since Ronald Reagan.
To say that those who believed otherwise and whose votes were split among 16 candidates do not reach the numbers of the plurality that gave us this nominee, especially in the midst of the disinformation campaign waged against that leading opposition candidate may provide you with a distorted metric.
Those who decide to build a third party do not expect instantaneous gratification. The American people have forgotten what it is like to be free, and sometimes have given up that freedom by popular demand. It may take the bitter lash of totalitarianism to awaken their desire for freedom. I, for one, hope not, and seek to provide my children, grand children, and great grandchildren another option.
Even if you feel you must vote for Trump to keep Hillary out of office, let me ask you, Are you confident that this will lead to the government you want, that you think America should have? If not, do what you feel you must this time, but help build a party which will fight for the America that should be for all Americans, not just some bitter dregs and tossed bones from a ruling elite.
YMMV