The Rep Party, if it still is one party anymore, is in this position because:
- Trump is articulating the need for action on issues that should have been resolved by Congress a long time ago and which are of deep concern to the American people regardless of party affiliation or ideals
- The Reps obstructed legislation that would resolve some of these serious problems with an eye towards winning the Presidency and both houses of Congress to advance a conservative agenda after the elections, while tailoring the election process to give more weight to the early frontrunner
- They stoked anger against the Dems, but underestimated the extent to which Rep voters were angry at their heavily-funded Rep candidates, who were viewed as establishment. Trump's insults of his fellow candidates touched a cord - "lying", "cheating", "not smart", "spoiled", "like a little boy", "pathological", "a fraud" - in enough Rep voters to get him the nomination.
- Trump offers solutions, simplistic perhaps, but a hope for change even if he borders on authoritarianism - China will negotiate a new trade deal, Mexico will pay for the wall, the Congress will be made to do what he wants - or there will be tariffs, mass deportation, problems with Congress, etc.
- The usual strings that control candidates - money - are not there with a self-funded candidate.
Now the question is whether Trump represents the Party, its ideals and message and what to do about it if he does not. If he wins, he could take over the Party, subvert their ideals, and lead them in an undesirable and untenable direction.