Place all the blame on the voters who didn't roll over and vote for a party that doesn't stand for anything they believe in anymore. And yet somehow it's the voters' fault the party changed and so did their vote.
Well, it IS, in part, the voters' fault.
See, every party activist, every politician, every canvasser, even every President, is a citizen just like you and me. We don't have an official Nobility, though of course it sometimes appears so. There's something each of us could have done, but didn't.
So if you (colloquially -- I don't know what YOU specifically did or didn't do) sat on your butt and waited for the political parties to offer you some great candidates, then it's your fault, too. You could have gotten involved years ago, if you'd have bothered.
So now you're stuck with a choice between an unpalatable R or D, and a futile vote for a Libertarian who won't get elected, or even get included in debates. But it's not
your fault. It's
their fault for not providing you with a wonderful candidate so you could spend 20 minutes out of every two years filling out a ballot, then 20 minutes a day the rest of the time, bitching.
Uncle Sam wants YOU. Without you, what can we do? "They" won't do it.