I generally agree that the Republicans saying "this doesn't represent me" no longer have reasonable basis for that argument.
As others have said, on any given individual election, I can imagine voting for someone who ends up being different than you expect. You thought you elected a moderate, you instead elected an extreme xenophobe, or something. Accidents happen, and no single elected official can perfectly encapsulate your views.
But when these people are elected en masse and over several election cycles, that explanation loses its plausibility. You essentially have to argue that you just so happen to keep voting for extremists by accident every year across a wide variety of elected positions.
In a very literal sense, the Republican party does represent you if you keep voting for them. You cannot plausibly say, "This isn't who I thought I voted for" when that keeps happening over several cycles all across the country in a variety of elections.
I agree with you there. Although I do feel that some people just vote the party line, because it's the team they feel they have to vote for. I posted this a couple pages back, but I really do feel like people view it as: this party is good, this party is bad. And in America people really identify themselves with their political parties.
I personally know people that will vote Republican, even if they can't stand the candidate, just because they feel ideologically they can't support the Democrat opponent. So even if they don't think the candidate running represents them, they will still vote for them. I don't think this is a valid excuse though, and they share the blame for continuing the party in a direction that isn't what they want. The whole team mentality with political voting is just dumb.
Although sadly, I think there are a lot of voters on the right, who do want the batshit crazy things these people are touting. They must exist, or why would they be running on these platforms? So either the majority of the party supports this, or the system is set up in a way that only in the places that matter (ie. the districts where these people keep their jobs), is where these extremists are the ones that voting. I'm not sure that means they are the majority of the party's voters though. But they certainly hold the most power, since they are the ones who decide who keeps their job or not.
EDIT: I do agree with you though. I don't think it's an excuse if you keep voting for them. I guess i just wonder if the majority of the voters in this party support what is being sold, or if it's a loud minority that controls the power based on districting.