CHARLESTON, S.C. (AP) - No joke: comedian Stephen Colbert's sister is running in earnest for a vacant South Carolina congressional seat.

Campaign manager Bill Romjue said Friday that Elizabeth Colbert-Bush plans to file next week and make a formal announcement. She did not immediately return messages from The AP.

Colbert-Busch will file as a Democrat seeking the 1st District seat left vacant when Gov. Nikki Haley appointed Tim Scott as the state's newest U.S. senator. Colbert-Bush is a Charleston native like her brother and development director at the Clemson University Restoration Institute in nearby North Charleston.

One other Democrat and at least 10 Republicans are seeking the seat along South Carolina's south coast. GOP candidates include former Gov. Mark Sanford.

The primaries are March 19, runoffs on April 2 and special election May 7.