Until relatively recently, our political parties were constantly splitting up, realigning, and reforming. The Federalist party broke up and vanished after the War of 1812. The Democratic Party split over the leadership of Andrew Jackson, eventually creating the Whig party. The Whigs broke up in the 1850s over the issue of slavery, and the Republican party emerged. Republicans split in 1896, and again in 1912 as the Bull Moose Progressives followed Theodore Roosevelt out of the GOP. Southern Democrats split with their party over civil rights in 1948, 1960 and 1968, before ultimately migrating to the Republicans.

But for the past 50 years, politically active Americans have sorted themselves into two teams, and two teams only, no matter how much they differed with other members of their own team. There is political logic in this. Splitting your voters leads to defeat. But at some point, principle must come before a desire to hold on to power.

And now Republicans who have defied Trump actually have a political incentive to split because Trump and his followers are coming for them with censure motions and primary challenges. Those few Republicans who have broken with the party have crossed the Rubicon. Trying go back now and profess your loyalty and beg for forgiveness is a fool’s errand. Ask Jeff Sessions how that worked out for him. During his losing primary campaign to regain his seat in the Senate, he tried to argue what a loyal Trumpist he really was, while Trump viciously attacked him. These rebel Republicans may not want a civil war, but that war has already started, and they need to fight back.