For once a presidential jaunt can truly be called historic. Having restored diplomatic relations with Cuba after a 54-year freeze, today and tomorrow Barack Obama is in Havana, setting the seal on his boldest foreign-policy act. Apart from meeting his counterpart, Raúl Castro, he will watch a baseball game, talk to dissidents and budding entrepreneurs, and make a speech portraying a freer Cuban future. Mr Obama’s bet is that engagement will do more to hasten economic reform—and eventually political change—on the communist island than did the embargo. He has eased travel and the use of the dollar. Starwood Hotels has announced a landmark investment; expect other business deals too. But watch out for ambushes: Elizardo Sánchez, one of the dissidents invited to meet Mr Obama, was briefly arrested on Saturday, and, just hours before the president’s arrival, police detained protesters from a group of political prisoners’ wives. Is that the party spirit?