He is now. This is what's been stewing beneath the surface for decades, growing stronger and more urgent, especially with the advent of the first black presidency. And it is the outcome of a bit of a coup, but the party has been allowing some of its activists to wink and nod at the very elements that now run the show. It stands to be a very inauspicious and ironic end to the Party of Lincoln.
If you are correct that Trump is now the Republican Party then I agree, the GOP is dead. Now it is the Trump Party. History will show whether Trump killed the GOP or whether he is a small flash in the pan, forgotten by 2020.