Two days before registered Republicans voted in the party’s primary election in Kentucky’s 4th Congressional District on May 20, Donald Trump called the incumbent representative, Thomas Massie, “the worst Republican congressman in history”.

Massie subsequently lost the primary to a political newcomer with no prior office-holding experience. Ed Gallrein’s not-so-secret weapon was that he had the backing of the US president.

Just over a week later, Texas voters were asked to decide whether 22-year Senate veteran John Cornyn should be ousted in favour of the state’s attorney-general, Ken Paxton – who was also endorsed by Trump. Despite all the baggage Paxton carried into the race: an indictment for fraud (charges were later dropped) and an impeachment for bribery, which he denied before being acquitted in the state senate. He has also gone through an acrimonious divorce accompanied by accusations of adultery (which he has also denied), Paxton won the May 26 primary handsomely with more than 60% of the vote.

Trump has long threatened to “primary” – back a rival candidate in the upcoming primary election – Republicans who displease him in some way. But with the midterm elections looming in November, we’re seeing this put into practice. And it’s making the conservative “old Republican” wing of his party very nervous.

America’s high-profile November elections involve straightforward contests between the nominees of the main parties. But before a candidate can represent their party, they must........

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