AP Photo

Nigel Farage is the kind of politician who apparently needs an opponent to bring out the best in him. Right now, that role is being played by a cushion. Sitting on a sofa in a London hotel lobby, Farage alternately slaps the cushion with the palm of his hand and punches it with his fist as he talks about how he intends to stir up British politics.

Farage is the leader of the United Kingdom Independence Party (UKIP), a right-wing conservative movement that aims to lead Britain out of the European Union.

For months now, his proposals have put the government on the back foot -- and this has rapidly increased his party's popularity among voters. Recent surveys show UKIP polling around 15 percent, which would make it the third most important political force in...