Republican leaders are so far refusing to telegraph their strategy for combating President Obama’s unilateral action on immigration. But they’re under enormous pressure from the right to act fast. Speaker John Boehner (R-Ohio), Majority Leader Kevin McCarthy (R-Calif.) and Majority Whip Steve Scalise (R-La.) have no shortage of options. The question is whether any of them would stop Obama in his tracks. Aides to GOP leadership say one weapon in their armory would be for Republicans to sue the president, either by expanding the GOP’s current lawsuit against him on ObamaCare or bringing new legal action. Republicans, who will take...