U.S. Rep. Julia Letlow, a Republican from Louisiana who had been encouraged by President Donald Trump to launch a primary challenge against incumbent Sen. Bill Cassidy, announced on Tuesday that she is indeed challenging the two-term senator -- setting up a new potentially contentious Republican primary and another test of the power of Trump's endorsement.

Republican Sen. Bill Cassidy of Louisiana, a frequent critic of President Trump, now officially faces a primary challenge.

"I have fought alongside President Trump to put America first, standing up for our parents, securing our borders, supporting law enforcement, rooting out waste, fraud and abuse that drives up inflatio...