In this Oct. 14, 2008 file photo, Sen. Susan Collins, left, and Rep. Tom Allen, begin their fifth debate in Portland, Maine. As an anti-Bush, anti-Republican wave swamps many of party's House and Senate candidates, Collins - a moderate often at odds with the party - appears to be riding it toward a third term. (AP Photo/Pat Wellenbach, File)

In this June 21, 2007 file photo, Sen. Susan Collins, R-Maine, makes her way to a vote on Capitol Hill in Washington. (AP Photo/Lauren Victoria Burke, File)