On Thursday, Trump endorsed Wyoming legislation that would prevent crossover voting in a primary election. Were the law to pass, Democrats, Republicans, or independents would no longer be able to switch party affiliation on the day of the state’s primary to vote for a candidate in another party.

The bill, introduced by Republican state Sen. Bo Biteman, is part of a push by some Republicans in the state to oust Cheney by blocking Democrats from switching parties to support her in her upcoming election against Trump-endorsed congressional candidate, Harriet Hageman.

Behind the scenes, Trump and Club for Growth’s David McIntosh have both personally called Wyoming’s Republican governor, Mark Gordon, to encourage him to back the bill, according to two people familiar with the calls.