Columbia, South Carolina (CNN) State Sen. Vincent Sheheen will be endorsing and campaigning for Martin O'Malley in South Carolina, CNN has learned, according to the campaign.

Sheheen, a Democrat, ran against Republican Gov. Nikki Haley in an unsuccessful gubernatorial bids in 2010 and 2014. But Sheheen holds a prominent Democratic position in statewide politics, given than the Legislature is overwhelmingly controlled by Republicans.

The O'Malley presidential campaign is set to release a list of staffers and political chairman on Thursday, according to an advance copy of the release obtained by CNN.

O'Malley belatedly joins Hillary Clinton and Bernie Sanders with paid campaign staffs in the first-in-the-South primary state. He will have two paid staffers in South Carolina.

"Vincent is a big get. Not only is he the most popular Democrat in South Carolina, but he's a sitting state senator and has the most up to date and expansive voter file in the state," said Boyd Brown, a former state representative and state political co-chair for O'Malley, in the release. Brown's role with the campaign was also announced Thursday.

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