Left-over campaign contributions can remain in PACs, go to charities or foundations.
"There's a wide gap, if not a gulf, between what lawmakers can do with regular campaign money versus leadership PAC money," said Dave Levinthal, communications director for the Washington, D.C.-based CRP. "The question comes up: What can politicians do with the leftover PAC money, and the answer is pretty much whatever they want."
Source: http:// abcnews.go.com/Business/campaign-finance-senators-house-members-campaign-funds-retire/story?id=10203316