What happens to "super PACs" after their candidate has dropped out of the race? They become zombie PACs. They won't eat your brains, but they still could impact elections in the coming months.
Usually when a candidate drops out of an election, there are restrictions on how the leftover campaign money can be used. But as long as the money from super PACs are not directly involved with a candidate's political campaign, the money can be used in any manner — even personal expenditures like yachts or a rough day at the blackjack table.
In Rick Santorum's case, the "Red, White, and Blue" super PAC that was originally supporting him could shift towards the general election, running ads against President Obama, or getting involved in congressional elections. And some super PACs have already shifted to supporting Romney's campaign, like a super PAC formerly associated with Michele Bachmann.
Kim Barker covers campaign finance for Pro Publica, a non-profit investigative news organization.