The comprehensive immigration reform bill that has dodged attacks from the left and right for weeks, survived “poison pill” amendments, and was once pulled from the Senate schedule failed its most important test Thursday. Passage of the legislation now appears unlikely. The bipartisan coalition that had shepherded the measure through so many obstacles failed to get the 60 votes necessary to end debate. The final vote was 46-53 Until Thursday morning, it was unclear whether the bill would survive the cloture vote. But in the end, opponents of the measure from both sides of the political spectrum gained enough support...