BIRMINGHAM, Ala. — The “southern firewall†Ted Cruz’s presidential campaign has been building for months appears to be crumbling under the weight of Donald Trump’s staying power and Marco Rubio’s resurgence. The Cruz campaign told Yellowhammer Wednesday night they are pulling out of the Presidential Forum set to be held at Samford University in Birmingham on Saturday, and will not be holding any other events in Alabama ahead of election day. Senator Marco Rubio’s campaign, however, reiterated their commitment to the event. The move is one of the most open indicators to date that Cruz has failed to pick up...