BOSTON (AP) — Edward Markey's rise to the U.S. Senate is officially kicking off the start of the already crowded special election to fill the 5th Congressional District seat he had held for the past 37 years.

Markey on Tuesday was sworn into the seat that John Kerry won in 1984 and held until he resigned earlier this year to become secretary of State.

A number of candidates have already begun campaigning for Markey's old House seat.

The Democratic candidates include Middlesex Sheriff Peter Koutoujian, Melrose state Sen. Katherine Clark, Medford state Rep. Carl Sciortino, Belmont state Sen. William Brownsberger and Ashland state Sen. Karen Spilka.

Republican attorney Frank Addivinola also is running.

Patrick on Monday set the dates for the special election.

The primary elections will be Oct. 15. The general election is Dec. 10.