In late spring of 1974, Washington newspapers were crammed with headlines about Watergate and impeachment. But President Nixon was 6,500 miles away in Saudi Arabia, in the middle of an ambitious 10-day, seven-stop foreign trip. His ill-fated mission — derided by critics as "impeachment diplomacy" — holds a lesson for President Trump: While successes in foreign policy can help distract from troubles at home, domestic problems can also spill over into foreign policy and have long-reaching consequences.