During the campaign, then-Sen. Barack Obama made light of what he saw as his predecessor-to-be's lack of diplomatic skill. As Wednesday's U.N. Security Council vote on sanctions over Iran's nuclear program showed, Mr. Obama's team could learn a few things about diplomacy from George W. Bush. The vote sent "an unmistakable message" to Iran about the international community's commitment to stop nuclear proliferation, according to the White House. The vote tally also communicated a secondary point: President Obama is losing the international consensus that Mr. Bush once had. In three rounds of Bush-led U.N. votes on sanctions from 2006 through...