A Republican senator who broke from his party to vote in favour of convicting US President Donald Trump in impeachment proceedings during his first term is facing a bruising primary challenge in his home state of Louisiana. Bill Cassidy’s primary race on Thursday has been seen as a barometer of Trump’s continued hold over the Republican Party. Even as polls have shown the president’s approval tanking, early primary votes have shown the continued weight his endorsement carries. Recommended Stories list of 3 items list 1 of 3 Pentagon gives new $29bn Iran war price tag, downplays munitions concerns list 2 of 3 ‘Cotton picking’: US lawmaker condemned for racist comment about Jeffries list 3 of 3 Trump faces slew of ‘bad options’ on Iran as diplomacy falters end of list Trump has backed US Representative Julia Letlow in the Senate race. State Treasurer John Fleming is also running. The winner of the Republican primary is all-but-assured to win in the general election in the deep-red state.…