One guy - not even Trump - is going to take down a party. The Whigs dissolved because they wouldn’t take a stand on stopping the expansion of slavery. Republicans may dissolve over the issue of immigration.
The new Republican Party had the backing of some of the Big Media of the day (Horace Greeley’s New York Daily Tribune), and the backing of some already popular politicians (western hero John Fremont). Lots of analogies.
You’re right. One person can’t take down a party. But several million of his supporters can.