On Sunday, Louisiana senator Bill Cassidy lost his right to run as a Republican in the US midterm elections. President Trump ensured that the insufficiently loyal senator, who voted to convict Trump in his 2021 impeachment trial, was replaced in the state Republican primary by a guaranteed loyalist.On Tuesday, in Kentucky, he continued the process of copperfastening his absolute control of the party with the defeat of his chief antagonist in the House of Representatives, Thomas Massie, after the most expensive primary on record – political support groups spent more than $33 million on ads in Kentucky’s fourth district.Massie, a libertarian maverick and all-too-rare party dissident, had voted against Trump’s tax cut bill, denounced the Iran war, and demanded the release of the Epstein files, qualifying , as the increasingly unpopular president put it, for the distinction of “the worst congressman in the history of our country.” For Trump, the ongoing primaries are the opportunity for revenge, as much as candidate management, and he has ensured that those running in states like Indiana and Louisiana took on Republican incumbents considered disloyal, particularly those unwilling to push through the district gerrymandering key to having any chance of retaining the party’s narrow control of the House.On Tuesday, Trump also endorsed Texas’s attorney-general, Ken Paxton, over incumbent two-decade senator John Cornyn who, the president claimed, “was very late” to endorse him in the 2016 presidential campaign. The move has prompted warnings from within the otherwise largely loyal Senate majority – currently 53 to 47 – that Trump is jeopardising a vulnerable seat now held by a popular senator.The primaries are in reality a sideshow to the real battle for control of Congress ahead of November’s vote, through the widespread redrawing of maps and “redistricting” ordered by Trump and facilitated by the US Supreme Court. This may yet give him sufficient seats in the absence of a popular majority.