Most expensive re-election campaigns Most Expensive Re-Election Campaigns President Barack Obama has announced he'll run for office again in 2012, launching speculation about how much he'll spend. We've rounded up past incumbents who spared no expense in defending their political posts. Barack Obama The president has officially announced his 2012 re-election campaign, and some say it'll be the most expensive in history. What is the early fundraising rumor? Michele Bachmann Last November, U.S. Rep. Michele Bachmann, R-Minn. beat her challenger to retain this congressional district. The race earned a high-dollar distinction. Barbara Boxer In last year's U.S. Senate race, U.S. Sen. Barbara Boxer, D-Calif., beat her wealthy opponent. It's been reported that the senator spent nearly everything she'd raised — how much was that? Michael Bloomberg Bloomberg was named mayor of New York City the third time in a row (how did he do that?), having bested hi...