Republican Sean Bielat is the latest candidate to enter the special Senate election in Massachusetts while former U.S. Attorney Michael Sullivan is expected to announce soon whether he's also in the running on the GOP side.

Bielat has filed papers with the Federal Election Commission to form the Sean Bielat for Senate committee.

Bielat has run twice for Congress in the 4th Congressional District. He lost in 2010 to former Democratic Rep. Barney Frank and last year to Democratic Rep. Joseph Kennedy III.

Former Plymouth Republican state committee member Christopher Fava said Sullivan was expected to make an announcement as soon as Thursday.

Norfolk State Rep. Daniel Winslow and Cohasset businessman Gabriel Gomez have said they are running on the Republican side.