Rep. Edward MarkeyEdward (Ed) John MarkeyDems lambaste Trump’s ‘outrageous’ EPA chemical safety pick Dems plan to make gun control an issue in Nevada Dem senator pitches ideas for gun control after shooting MORE (D-Mass.) announced Thursday that he plans to run in the special election to replace Sen. John KerryJohn Forbes KerryFor the sake of national security, Trump must honor the Iran deal Bernie Sanders’s 1960s worldview makes bad foreign policy DiCaprio: History will ‘vilify’ Trump for not fighting climate change MORE (D-Mass.).

“The events of the last several weeks — from the devastation of Hurricane Sandy and the tragedy at Sandy Hook Elementary to the fiscal cliff debate over tax giveaways to the rich, have all made clear that Massachusetts needs a Senator with the right priorities and values,” Markey said in a statement. “I have decided to run for the U.S. Senate because this fight is too important. There is so much at stake.”

A “Markey for Senate” website was already up and running on Thursday and soliciting donations. According to the Center for Responsive Politics, Markey will begin his campaign with $3.1 million on hand.

President Obama’s nomination of Kerry for secretary of State has set off a scramble — particularly among Democrats — to fill the Massachusetts Senate seat in the special election next year. Markey is the first candidate from either party to formally declare his candidacy.

Sen. Scott Brown (R-Mass.), who just lost his Senate seat in a tough race against Elizabeth WarrenElizabeth Ann WarrenOvernight Finance: Lawmakers grill Equifax chief over hack | Wells Fargo CEO defends bank's progress | Trump jokes Puerto Rico threw budget 'out of whack' | Mortgage tax fight tests industry clout Michelle Obama is exactly who the Democrats need to win big in 2020 Wells Fargo chief defends bank's progress in tense Senate hearing MORE (D), is widely viewed as the front-runner on the Republican side.

Markey is a longtime critic of oil companies, and is among the most prominent Capitol Hill advocates of imposing limits on greenhouse gas emissions and boosting green energy sources.

He co-authored the sweeping cap-and-trade and energy bill that narrowly passed the House in 2009, but went nowhere in the Senate. 

In the statement announcing his bid, Markey took shots at “the Tea Party-dominated Republican Party,” as well as “oil and coal lobbyists” looking to “thwart our clean energy future.” He also denounced “extremists” who want to “restrict women’s rights and health care."

The list of potential candidates on the Democratic side for Kerry's seat has been pared down considerably in recent days. 

Ted Kennedy Jr., the son of the late Sen. Edward Kennedy (D-Mass.), has said he will not run. Writer-director Ben Affleck and Massachusetts Attorney General Martha Coakley (D), whom Brown defeated in 2010, have also ruled out bids.

Victoria Kennedy, the second wife of the late Sen. Kennedy, has been mentioned as a potential candidate, and two other Massachusetts Reps., Stephen Lynch (D) and Michael Capuano (D), have mentioned passing interest, according to various media reports.

A spokesman for state Sen. Ben Downing (D) told The Hill on Friday “it’s definitely something he’s considering.” Downing released a statement congratulating Kerry on his nomination and saying he “will be meeting with people throughout the Commonwealth” as he considers a run.

According to state law, Mass. Gov. Deval Patrick (D) must first appoint a temporary successor to serve before the special election, which will take place about five months after Kerry leaves the seat, if he is confirmed for the State Department post.

Ben Geman contributed.

This story was last updated at 4:14 p.m.