President Barack Obama's return from last week's G8 summit and a star turn in Ghana could test one of the great truisms of US politics: When things get tough at home, go abroad.

Foreign trips have been political bonanzas for presidents since Richard Nixon. Famous for startling the world when he came to Beijing to meet China's leaders and open a new era in Sino-American relations, Nixon used foreign trips many times to bolster his standing at home. When issues from Vietnam to Watergate to soaring inflation pushed his poll numbers down and weakened his ability to deal with Congress, he could always count on a visit to Soviet leader Leonid Brezhnev or Egypt's Anwar Sadat to remind TV-watching Americans of his stature as a world leader.

Most presidents since then have profited from such international-stage management.