Former Hawaii Gov. Linda Lingle is expected to announce today that she is running for Senate, giving Republicans their top recruit and perhaps only legitimate contender for the open seat.

Lingle had been expected to announce her decision for the seat of retiring Sen. Daniel Akaka (D) after the third fundraising quarter concluded, and the Honolulu Star-Advertiser reported late Monday that she would do so at a luncheon of the Sales and Marketing Executives International at the Pacific Club at 6 p.m.

Republicans hope her entrance at the very least expands the map for the Democratic Senatorial Campaign Committee, which is defending 23 seats this cycle compared with 10 seats for Republicans. Adding another competitive state to the list would spread the committee’s resources even thinner.

However, besides Lingle’s two terms as governor in the past decade, Republicans have had little success in the Aloha State in recent years. And with President Barack Obama on the ticket in the state where he grew up, the winner of the Democratic primary will have tremendous coattails to ride. Obama won 72 percent in the state in 2008.

Rep. Mazie Hirono and former Rep. Ed Case are running for the Democratic nomination, and the winner will be the favorite going into the general election. Hirono so far is the candidate with more establishment support, including from Sen. Daniel Inouye (D), who remains upset with Case for challenging Akaka in 2006.

But Lingle, despite approval ratings that went upside down toward the end of her second term last year, will make Hawaii a state to watch.

Roll Call currently rates the Hawaii Senate race as Likely Democratic.