Two politicians go to a bar and order two glasses of vodka on the rocks. The first politician quickly empties his glass, then orders a second one, a third one... The second politician patiently drinks his own vodka, but about 20 minutes later, he drops down dead. The police discovered that the barman tried to assassinate both politicians, but how come the second one died and the first one lived?
The poison was in the ice cubes, so the second politician drank them when they melted in his drink.