“The Republican vote would be split and the Democrats would win the White House for the next 20 years.”
That’s only true if you assume a new party would not also draw votes from Democrats, and also assume that the Republican party would remain at all viable if the majority of their voters left.
This is how the deep state stays in power. The Democrats AND the republicans ARE the deep state. They're playing you to keep out alternatives.
What evidence do you have that the GOP has done any "winning", even when they've held the executive and legislative branches? I see the Democrats doing a lot of winning, and in the process destroying the country. If a GOP that actually paid attention to their party platform and listened to their voters were winning, we wouldn't be in the mess we are in now. The GOP deserves to die at this point (the party, not the voters) because they are a party about nothing.
If the Republican failed to do so, the third party would put it out of business.
Anyone not willing to go to those measures is voting is allowing the Republican establishment to continue to sellout its base year and after year.
The definition of insanity is doing that same thing over and over again and expecting a different result.