Senate Democrats are making plans to force a floor vote on legislation that would invalidate Arizona’s controversial immigration statute if the Supreme Court upholds the law this summer. Sen. Charles E. Schumer (D-N.Y.) will announce the fallback legislation at a hearing on the Arizona law Tuesday, a day before the Supreme Court hears oral arguments in a suit to determine whether Arizona had the authority to enact the 2010 state crackdown. The legislation would have little chance of passing in a stalemated Senate or being approved by a GOP-held House, but it would allow Democrats to push their electoral advantage...