Ann Coulter says Republicans shouldn't waste their time defending their incumbents or primarying them, just vote for the Democrat

 Spending energy, time, volunteers [on primaries] is a zero-sum game when it comes to campaigns. We can not waste our time defending incumbents. As bad as Republicans are, there are a lot of bad Republicans, but there are no good Democrats. So do not primary an incumbent. Do not waste the time and money.

Here.