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 launch a primary battle against incumbent GOP Sen. Bill Cassidy, a source familiar with the matter said. Letlow was elected to the House in