...That more and more emphasizes the importance of defeating the other party, than in actually passing legislation or governing in a way you find desirable.
And no, saying 'In order to pass X/do Y, we need to defeat the other party!' doesn't circumvent this.
The Establishment currently seems bewildered, and a bit scared, that the mere defeat of the opposing party is no longer enough of a prospect to motivate their would-be supporters. It turns out these voters want some action. And not just failed, half-hearted attempts, but victories.