For the third time in only four years, Massachusetts voters will go to the ballot box this summer to choose a new U.S. Senator. The special senate election on June 25, after primary elections on April 30, will decide who will fill the seat left vacant by last week’s confirmation of Secretary of State John Kerry.

Former U.S. Senator Scott Brown, the republican who was elected in the 2010 special election to fill Senator Ted Kennedy’s seat and recently lost his 2012 reelection bid to Senator Elizabeth Warren, has declared he will not be a candidate in this race.

“I was not at all certain that a third Senate campaign in less than four years, and the prospect of returning to a Congress even more partisan than the one I left, was really the best way for me to continue in public service at this time,” Brown said in a statement on his website.

A host of other candidates with big name recognition have also declared their desires not to run, including Massachusetts Attorney General Martha Coakley, former republican gubernatorial candidate Charlie Baker, Mitt Romney’s eldest son Taggart Romney, and former democratic U.S. Representative Barney Frank.

Only two democrats have officially declared their candidacies: U.S. Representative Stephen Lynch and U.S. Representative Ed Markey. Lynch has been endorsed by a few labor unions, while Markey has been endorsed by many politicians including Sec. Kerry, former Rep. Frank, Mass. AG Coakley, and two dozen State Congressmen.

Marisa DeFranco, an immigration lawyer who ran in the democratic primary against Sen. Warren in 2010, announced on her official Facebook page today that she is looking for volunteers to gather signatures as she is “considering a run.”

On the republican side of the ticket, only former Nantucket selectman Doug Bennett has officially declared a bid for the seat. According to Cape Cod Today, Bennett, a vocal Ron Paul supporter, has lost twice in elections for Boston City Council but will run on his libertarian policies as a republican this cycle.

Republican State Representative Dan Winslow announced today to the Boston Herald that he is forming an exploratory committee to “test the waters for U.S. Senate.” In an interview with the Herald, Winslow said, “I have been disgusted by the partisan gridlock in Washington, D.C., and we have a record of proven bipartisan work here in Massachusetts.” The State Rep. added that he is confident that he can get the 10,000 signatures required by April 3 to get on the ballot but is weighing if he can “mount a credible winning campaign.”

Independent Jack E. Robinson, who announced his candidacy yesterday, has run unsuccessfully as a republican for several offices in the past decade, including U.S. Senator, Secretary of Commonwealth, and U.S Representative.

Robinson told the Boston Globe he is running because “extremism from both parties is preventing the 21st century from being the new American century. As an independent, I can bridge the gap in Washington and be a voice of the people and not of a party.”

Libertarian Daniel Fishman, who first ran for elected office in a failed bid for U.S. House seat in 2012, also announced his candidacy. On his campaign website, Fishman said, “I believe in a system where I can be for me, and you can be for you, and that doesn’t have to mean we’re against each other.  And when the time comes for us to work together, we can do so willingly.”

With no blockbuster names on the ticket, the race seems very unpredictable at this point. Rep. Markey, currently the longest serving Mass. state congressman, has the most name-recognition and big endorsements but still remains relatively unknown to the average voter.

In a statement released by his campaign, Markey has called for a “People’s Pledge” on banning third-party campaign donations, such as those from Super PACs.

“This race should be about the people of Massachusetts having a voice in the Senate, not the special interests,” Markey’s statement said. Lynch told the Boston Herald he will follow suit and denounce outside spending in the race. Republican candidates are expected to make similar pledges.