Former Hawaii Gov. Linda Lingle (R) will announce her Senate campaign Tuesday afternoon, according to the Honolulu Star Advertiser, potentially putting another Democratic-held seat in play and further complicating Democrats' plans to keep control of the Senate.

Lingle, a two-term former governor who won her second term with 63 percent of the vote, is the only Republican candidate in Hawaii who could have made this race competitive, especially in a presidential year when favorite son President Obama will be on the ballot.

She governed at times as a centrist, pushing for renewable energy development and supporting some abortion rights. But Democrats point to her strong backing of Sen. John McCain (R-Ariz.) and his running mate, former Alaska Gov. Sarah Palin, as evidence that Lingle isn't as centrist as she claims to be.

"Today marks Linda Lingle's biggest announcement since she nominated Sarah Palin for vice president, an event that typified Lingle's partisan Republican approach to governing," Democratic Senatorial Campaign Committee spokesman Matt Canter said in a statement. "Now Lingle wants to go to Washington to become a rubber stamp for Mitch McConnell and the Republican Party whose sole priority is to defeat President Obama at every turn."

Former Rep. Ed Case (D-Hawaii) and Rep. Mazie Hirono (D-Hawaii) are vying for the Democratic nomination to replace retiring Sen. Daniel Akaka (D-Hawaii). Most of the Democratic establishment in the state is lining up behind Hirono and against Case, a centrist Blue Dog who angered many with his 2006 primary run against Akaka. Lingle narrowly defeated Hirono in 2002 to become governor.