"In a political world reliant on a constant source of campaign cash, money can be power, and many sitting lawmakers have been stockpiling checks since they came into office. Most of the time, they are keeping it to scare off or prepare for potential challengers or to finance an ambition for leadership or higher office.
Sen. John Thune is a typical example. The South Dakota Republican, a potential 2012 presidential candidate, has $7.2 million in his campaign fund, according to the latest reports, which cover the period through the middle of November. Thune was unopposed this year, but he still raised $6 million and spent about half of that."
Despite record spending, politicians still have $400 million in campaign funds
Washington Post:
