Nate Silver at FiveThirtyEight has a well written post on how to whip up votes in a legilative body like the U.S. House of Representative: FiveThirtyEight: Politics Done Right: Time to Start Counting Yes Votes.
From time to time in the news you will hear that so-and-so is the Whip for such-and-such a party, and you may wonder: well, that’s an odd sounding job, what do they do? The obvious answer is they persuade people to vote a certain way on a certain piece of legislation before them. But how they go about it is very likely the way it is described in Silver’s post.
How they hand out carrots and swing sticks is another story. But it is very likely how they get the votes.