With Trump’s backing, Rep. Julia Letlow launches a primary challenge against Louisiana Sen. Bill Cassidy

By Arlette Saenz, Sarah Ferris, Eric Bradner, CNN (CNN) — Republican Rep. Julia Letlow has launched a run for US Senate in Louisiana, taking advantage of President Donald Trump’s endorsement to wage a primary battle against incumbent GOP Sen. Bill Cassidy. “Today, I am announcing my candidacy for the United States Senate to ensure the