(CNN) - Lamar Alexander, the third-ranking Republican in the Senate, will make a campaign appearance Friday in Delaware with GOP Senate candidate Christine O'Donnell, CNN has learned.
The Tennessee senator is the first member of the Senate Republican leadership to appear with O'Donnell, according to an Alexander aide.
O'Donnell stunned and disappointed the GOP establishment when she beat Rep. Mike Castle in the Republican primary. Castle was considered a sure winner in the general election, but O'Donnell now trails her Democratic opponent Chris Coons by double digits.
So why campaign for her now?
Alexander "is known in the caucus for getting along with people from the right and left and he's always working to get everyone on the same page," said the Alexander aide.
"Christine O'Donnell's election will help provide a badly needed check and balance on a runaway federal government that has given us too much spending, too many taxes, too much debt, and too many Washington takeovers," Alexander said in a statement posted in the endorsements section of O'Donnell's campaign web site.
At the 9am event at Buckley's Restaurant in Centerville, Alexander will thank O'Donnell's volunteers and supporters and he will hold a press conference.