The White House has put special operations strike forces on standby and moved drones into the skies above Africa, ready to strike militant targets from Libya to Mali — if investigators can find the Al Qaeda-linked group responsible for the death of the U.S. ambassador and three other Americans in Libya. But officials say the administration, with weeks until the presidential election, is weighing whether the short-term payoff of exacting retribution on Al Qaeda is worth the risk that such strikes could elevate the group's profile in the region, alienate governments the U.S. needs to fight it in the future...