Sen. Lamar Alexander is running out of prominent Republicans from Tennessee who will back him. 

In the third announcement in as many months, the senator's campaign for re-election revealed that all former Tennessee Republican governors and U.S. senators will be joining Alexander as honorary co-chairs for his 2014 bid.

The newest list includes names that will immediately register with longtime followers of state politics. Former Senate Majority Leader Howard Baker, who was also chief of staff to President Ronald Reagan, is on it. So is former Sen. Bill Brock, who was also Reagan's secretary of labor. 

Additional Republicans include former Govs. Winfield Dunn and Don Sundquist, along with former Sens. Fred Thompson and Bill Frist, who also served as Senate majority leader. 

The announcement continues an aggressive pattern from Alexander to shore up support from the GOP establishment. Though no Republicans have publicly voiced thoughts of unseating the 72-year-old senator, Alexander hasn't shown any signs of shrugging off a potential primary challenge. 

In a news release, Alexander said he was honored to have the added backing from the group of former state lawmakers. 

"This is a great honor to have the support of men I deeply admire for their service to our state and to our party," Alexander said in a release issued by his campaign. 

In December, the senator announced Tennessee's top Republicans, including Gov. Bill Haslam, Sen. Bob Corker and every GOP congressman except Rep. Scott DesJarlais, would offer support to his campaign. In February, Alexander revealed that 13 former Tennessee Republican Party chairs would be supporting his bid for a third term. 

The senator has also said he expects to collect a total of $3 million in campaign cash at four separate events this spring.