(CNN) - Rep. Stephen Lynch will hold a news conference in Boston on Thursday to announce whether he'll run in the June 25th special election in Massachusetts to fill out going Sen. John Kerry's seat, a campaign spokesman for Lynch tells CNN.
As of now longtime Rep. Edward Markey is the only Democrat who's announced a bid. Markey's been endorsed by the Democratic Senatorial Campaign Committee, Kerry, and Vicki Kennedy, the widow of the late Ted Kennedy.
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Lynch is a social conservative Democrat from South Boston who's been flirting with a run the past two months. Earlier this month two other Democrats who were considering bids, Rep. Michael Capuano and state Sen. Ben Downing, decided against running.
On the Republican side, the big question is whether former Sen. Scott Brown will make a bid to return to the Senate, or instead run for governor in 2014?
"Brown is still in the process of deciding and discussing it with his wife and family. No talk on timing yet," said a GOP strategist in Massachusetts close to Brown, who insisted on anonymity to speak more freely.
In January 2010, then Republican state lawmaker Brown upset Democratic candidate Martha Coakley, the state's attorney general, in a special election to fill the final two years of the term of longtime Democratic Sen. Ted Kennedy, who died the previous summer. Coakley defeated Capuano in a multi-candidate Democratic primary.
Brown won the special election by five points over Coakley, but lost his re-election bid in November to Democratic challenger Elizabeth Warren by eight points. Around 2.3 million voters cast ballots in the 2010 special election, and nearly 3.2 million voting in last month's general election. A big question is whether the 2013 electorate will look more like that of the 2010 contest or that of last month's general election.
Last month President Barack Obama nominated Kerry, the longtime senator from Massachusetts and 2004 Democratic presidential nominee as his choice to succeed outgoing Secretary of State Hillary Clinton. The Senate overwhelming confirmed Kerry on Tuesday.
The state's Democratic governor, Deval Patrick, is expected to announce Wednesday a placeholder (who would not run in the special election) to fill the Senate seat in the interim.
Whoever wins the June special election would serve the final year and a half of Kerry's term and would then have to run again in 2014 for a full six-year term in office.
- CNN Chief National Correspondent John King contributed to this report