Katherine Marlea Clark (born July 17, 1963) is an American politician who has served as the United States Representative for Massachusetts's 5th congressional district since 2013.
 The district includes many of the northern and western suburbs of Boston, such as Medford, Framingham, Woburn and Clark's hometown of Melrose.
 She is a member of the Democratic Party.
 She was a member of the Massachusetts House of Representatives from 2008 to 2011, and a member of the Massachusetts Senate from 2011 to 2013.
Nicola Dickson "Niki" Sauvage Tsongas ( ; born April 26, 1946) is an American politician and the current U.S. Representative for Massachusetts 's 3 congressional district .
 From 2007 to 2013 she represented Massachusetts 's 5 congressional district , the district her husband Paul Tsongas served prior to being elected to the United States Senate.
 She is a member of the Democratic Party.
 Following John Kerry's appointment as Secretary of State, she was widely expected to run in the 2013 special election for the Senate seat once held by her husband; she put such speculations to rest when she announced her endorsement of Representative Ed Markey instead.
Carl Michael Sciortino Jr. ( ; born July 6, 1978), is an American politician serving as executive director of the AIDS Action Committee of Massachusetts.
 A Democrat from Massachusetts, he represented the 34th Middlesex district in the Massachusetts House of Representatives from 2005 to 2014.
 The district includes parts of Medford and Somerville.
 Sciortino was a candidate for the Democratic nomination in the 2013 special election to succeed Ed Markey as a U.S. Representative for Massachusetts's 5th district, but lost to Katherine Clark.
This is the electoral history of Ed Markey, a Democratic Senator from Massachusetts.
 He was previously a Democratic Representative from Massachusetts, representing the 7th and 5th districts.
 Markey was first elected in a 1976 special election to replace the deceased Torbert Macdonald, and was re-elected in every subsequent election.
 He was also the Democratic candidate, and winner, of the 2013 special election, for the United States Senate.
Sean Garballey (born February 22, 1985) is the current Massachusetts State Representative for the 23rd Middlesex District representing Arlington and West Medford.
 He was elected in a special election on 4 March 2008, after the incumbent, J. James Marzilli, Jr. won a 2007 special election for a seat in the Massachusetts Senate.
Gabriel Eduardo Gomez (born August 27, 1965) is an American politician, private equity investor and former Navy SEAL.
 He was the Republican nominee for the U.S. Senate in the 2013 special election in Massachusetts, to replace U.S. Secretary of State John Kerry.
 Gomez was defeated by U.S. Representative Ed Markey.
 Gomez has the rare distinction of having served as both an Aircraft Carrier Pilot and a Navy SEAL.
James L. Kay II (born December 19, 1982 in Woodford County, Kentucky) is an American politician and a Democratic member of the Kentucky House of Representatives representing District 56 since his June 24, 2013 special election to fill the vacancy caused by the resignation of Representative Carl Rollins.
District 6 of the Texas Senate is a senatorial district that serves a portion of Harris county in the U.S. state of Texas.
 The seat is currently held by Sylvia Garcia, who won a 2013 special election after the death of Senator Mario Gallegos, Jr. on October 16, 2012.
William N. Brownsberger (born March 21, 1957) is an American state legislator who serves in the Massachusetts Senate representing the Second Suffolk and Middlesex District which includes his hometown of Belmont, as well as Watertown, and parts of Allston, Brighton, Fenway-Kenmore, and Back Bay which are neighborhoods of Boston.
 From 2007 to 2012 he was a member of the Massachusetts House of Representatives.
 He was a candidate for the Democratic nomination in the 2013 special election to succeed Ed Markey in the U.S. House of Representatives.
William Maurice "Mo" Cowan (born April 4, 1969) is an American politician and lawyer who served as a United States Senator from Massachusetts in 2013.
 He previously served as legal counsel and chief of staff to Massachusetts Governor Deval Patrick.
 Patrick appointed him on January 30, 2013, on an interim basis to fill the vacancy left by fellow Democrat John Kerry, who resigned to become Secretary of State.
 He declined to run in the 2013 special election to complete the remainder of Kerry's term.
 He was succeeded by fellow Democrat Ed Markey.
 He is now the Chief Operating Officer of ML Strategies, an affiliate of Mintz Levin.

Question: Which Massachusetts Representative did Carl Michael Sciortino Jr. lose to in the 2013 special election?
Answer: Katherine Clark