If President Trump starts a new political party, The Patriot Party, after he leaves office, what impact will this have on the Republican Party?

Absolutely catastrophic in the short term. The result would be somewhat similar to the effect Teddy Roosevelt had on the Republican Party when he broke with Taft in 1912.

I estimate Trump’s control of the Republican electorate at about 40%. He has control of what I call the talk radio wing. They’ve been motivated by immigration and white nationalism, white grievance, “they will take our guns” nuttery and/or anti-SJW “own the lib” stuff since the 1990s.

The rest is, give or take –

  • 20% traditional Reagan conservatives (e.g. Mitch McConnell) who actually care about conservative small government dogma & philosophy but believe in democracy
  • 20% evangelical Christian conservatives (Ted Cruz), mainly single issue focused on abortion and anti-LGBTQ (styled as “religious freedom”). They are prone to support an authoritarian if he wins and does what they want.
  • 15% country club pro-business, pro-privatization G.W. Bush, McCain, Romney, lite-conservatives, also believe in democracy.
  • 5% moderate Kasich, Murkowski, Collins types. Also believe in democracy.

(So over half the Republicans don’t really gaf about democracy, in large part because they can never be convinced that votes from people or places they don’t approve of are legitimate voters)

The election would *mostly* be between Trump and Biden/Harris. The Republican nominee would be a Cruz or Rubio type, kind of irrelevant, the way Taft was in 1912.

Trump would get decent amount of electoral votes and the Republican Party would get disastrously pasted in the House and Senate as a result of splitting the Republican coalition.

The ratio of Republicans to Democrats Trump would pull would be probably 5 to 1. He would pull a few Tulsi Gabbard types from the Democrats but destroy the Republicans by taking that talk radio set away from them, which is at least a third of their party and probably closer to 40%.

In a bad-case scenario for the GOP, the map would look something like this:

I gave:

  • Trump the states which in 2020 voted for Trump with 60% or more and had at least 2 points stronger Trump margin in 2020 than in 2016.
  • Democrats any state where they won at least 45% of the vote in 2020, in which a 10–15% drop in the Republican share would be catastrophic. I see no Clinton-Biden state in which Trump would strengthen Republican chances or be able to win himself.
  • I gave Republicans the rest – states where they won both 2016 and 2020 and Trump declined a bit or stayed even with 2016, and Democrats failed to get over 45%. Iowa was right on the bubble at 44.9% so I counted it a tossup.

Republican senate and House seats would be lost like crazy. The Republicans would recover after the Trump effect wore off like the way the Bull Moose Party faded out without Roosevelt. But in the short term, 4–8 years, it would be very very bad for them.