Louisiana primary voters could boot a sitting U.S. senator for the first time in nearly 100 years. Backing the insurgency against Sen. Bill Cassidy is President Donald Trump. The pair have been at political odds since Cassidy voted to convict Trump in his second impeachment trial more than five years ago. Liz Landers looks into the tight, three-way race.

Sen. Bill Cassidy of Louisiana faces two challengers — one endorsed by the president — in Saturday’s primary, five years after voting to convict Trump.

Louisiana voters will participate in a revamped and stripped-down state primary Saturday and decide the political fate of an embattled Republican U.S. senator targeted for defeat…