All parts always have several wings and voltages inside. Republicans are not unique or unusual in this respect. Its current factions are mostly in the so-called Freedom Caucus/Tea Party wing versus what this group ironically calls the establishment wing, which seems to be a euphemism for moderates.
You can choose multiple starting points for this break…you could probably go back to Barry Goldwater if you really wanted to. We could cite Pat Buchanon and his nativist movement. But the latest wave seems to start with the Tea Party.
The Tea Party began in the later stages of the second Bush administration as an anti-spending revolt against Bush, who was a very wasteful president. It has grown stronger as a faction opposed to Barack Obama. The Tea Party’s favorite tactic, rather than challenging Democrats, is to impose ideological purity on Republicans by challenging moderate Republicans with far-right opponents in the primaries. This tactic tends to push moderates to the right, but it also results in fewer Republicans getting elected, as these moderate Republicans are often found in very purple neighborhoods.
At some point, the Tea Party merged with, or was taken over by, the nativist wing of the Republican Party. And during the Obama era, these Republicans in Congress started calling themselves the Freedom Caucus, which is selfish but endearing. High-level members like Ted Cruz began pushing leaders toward self-defeating tactics like government shutdowns rather than accept small, slow progress.
And that’s important because progress in politics tends to be just that. You can rarely radically remake the status quo all at once. More often than not, you need to make gradual progress. Meticulously shifting the status quo bit by bit. The Democrats have been masters of this Long Con for nearly a century. That’s why they win. Meanwhile, Republicans seem unwilling to do the same, and the Tea Party is a part of it.