Republican state Rep. Dan Winslow announced Tuesday that he is making the first official moves to run in the special election for the Bay State’s open seat.

“Today I’m taking the necessary steps to form an exploratory committee to test the waters for the U.S. Senate,” Winslow said in a statement. “We need to fix a broken Washington where progress is being hampered by partisan gridlock. If we continue to elect the same Washington politicians, we can not expect different results.”

Winslow told The Boston Globe he was “99 percent there” on a run.

Winslow is the first Republican to take official steps toward a bid for the seat formerly held by Secretary of State John Kerry. In recent days, many other Republicans, including former Sen. Scott P. Brown, have taken their names out of contention.

Massachusetts Reps. Edward J. Markey and Stephen F. Lynch are running for the Democratic nomination for Senate.

Roll Call rates the Senate special election as Likely Democratic.