Republican U.S. Senate candidate and former Navy SEAL Gabriel Gomez speaks on April 4 in South Boston, Mass. On Tuesday, Gomez won the GOP nomination and will face Democratic Rep. Ed Markey in a June 25 special election.
But Brown opted not to run for Kerry's seat, and now it will go to either Rep. Ed Markey, a Democrat who has been a congressman for nearly four decades, or Republican newcomer Gabriel Gomez, a state businessman and former Navy SEAL.
Both won their party's primary races Tuesday, and will face off in the general election on June 25.
To get a flavor of current politics in Massachusetts, how the marathon bombing affected the primary races, as well insight on Scott Brown's political ascendency and decline, we turned to two prominent politicos from the state:
Rep. Ed Markey on Tuesday won the Democratic primary in the race to replace Sen. John Kerry.
Rob Gray, a Republican political consultant who was an adviser and strategist for Mitt Romney's 2002 gubernatorial campaign, and for Sen. John McCain's 2008 GOP presidential effort, and was press secretary to former Massachusetts Republican governors William Weld and Paul Cellucci.
And Warren Tolman, a Boston lawyer and former Democratic state legislator who ran for lieutenant governor in 1998, and for his party's 2002 gubernatorial nomination.
NPR: It wasn't so long ago that Democrats were fretting about Massachusetts Sen. John Kerry being tapped for secretary of state because of the prospect of Scott Brown running again. Did that concern seem warranted to you at the time, even given his bruising loss to Warren?
Gray: Democrats were right to worry. If Brown had opted to run in the special election he would have just been coronated in the GOP primary and he'd be comfortably leading Ed Markey in general election polling. Steve Lynch [Markey's primary opponent, a fellow Democratic congressman] either wouldn't have gotten in the race, or if he had he'd have performed better against Markey in the primary. Democrats would have seen him as having a better chance to beat Brown due to his appeal to blue collar independents, and he wouldn't be the easy target Markey is with four decades as a Washington insider.
Tolman: Of course Democrats were concerned about Brown. We took him too lightly once and paid the price. If you are a political person not concerned about beating a guy with national stature in a low turnout special election, we should check your pulse. Nonetheless, the dynamics of the current race would be very different if Brown ran — and Brown knew it. Markey or Lynch would have made the same arguments that were so successful for Elizabeth Warren: a vote for Brown empowers Senate Republicans. This is a very effective argument in Massachusetts.
Overcoming Party Affiliation
NPR: What is it about candidates like Scott Brown — or former Democratic Gov. Brian Schweitzer in the red state of Montana — that allows them to overcome built-in difficulties, including tradition and voter registration, and win? Or at least make the race initially competitive, as Brown did with Warren?
Tolman: Remember, Brown lost to Warren by almost 8 percent, or 260,000 votes. Given that he spent over $30 million and had a big head start, this is nothing to dismiss lightly. Brown won the  special election due to a "perfect storm." He came across as a likable guy, said he would be bipartisan, raised a ton of money by vowing to stop Obamacare and caught many Democrats sleeping as they thought the race was over after the primary.
Gray: Massachusetts is a majority independent state, with 53 percent of voters not enrolled in either party. [Among registered voters, Democrats hold a 3-to-1 advantage over Republicans.] Brown tapped into that dynamic in the 2010 special election. At that time, he was seen as a regular guy, and his personality and the lack of a strong campaign by his opponent allowed him to eke out a win. The 2012 election, with regular voter turnout instead of a subset in a January special election, brought that back to reality. His initial election turned out to be a temporary euphoria aided by the turnout math, a perfect storm of Obamacare opposition and the national money it brought into Massachusetts to help Brown win.
NPR: There's a heavy Romney flavor in the ranks of advisers for candidates in the Republican race. How do you see the lingering influence of Romney and his people affecting the general election race?
Gray: Unfortunately the general election looks like a long shot [for Republican Gomez]. There's a pretty small group of Republican operatives and campaign staffers here, so you'll see people who worked on the various Romney campaigns involved in campaigns here for quite some time.
Tolman: Given that it was Romney's team that helped Brown, and that these guys are the last two major Republicans to win in Massachusetts, I expect that we will continue to see Romney's presence felt until a new, major Republican is elected in Massachusetts.
State vs. Federal Races
NPR: Before Gov. Deval Patrick, a Democrat, was elected with more than 55 percent of the vote in 2006, Massachusetts had four consecutive Republican governors dating back to William Weld, who took office in 1991. They followed three Democratic governors. What does that tell you about politics in Massachusetts, where Kennedy was typically re-elected with 65-plus percent of the vote in all of those years. Or, more importantly, what does that tell you about the state's Republicans?
Gray: Massachusetts voters have always been more likely to vote for Republicans in state races rather than federal races. Federal issues and the national Republican agenda don't necessarily compute here — that's part of what caught up with Brown over time. A pro-choice, pro-gay rights Republican can easily get elected governor in this state, and there's a good chance one will in 2014 after Deval Patrick — an excellent candidate and campaigner — is no longer on the ballot. Voters here may be overwhelmingly Democratic in their federal election choices, but in state races there is a healthy appetite for balance, and a Republican governor can provide that. It's also a tribute to the success that Weld and his successor, Paul Cellucci, had in governing the state and turning the economy around.
Tolman: On the federal side, the national Republicans make it increasingly difficult for Massachusetts Republicans, and that is not changing any time soon. On the state side of the ledger, there were some unique characteristics to the Democratic and Republican victories. Let's face it, Bill Weld was more to the left of the political spectrum in many people's eyes than [1990 Democratic gubernatorial candidate] John Silber. And my running mate [1998 gubernatorial candidate] Scott Harshbarger had earned the wrath of many an otherwise good Democrat with some of his prosecutions and investigations. That allowed a popular acting Gov. Cellucci to eke out a very close victory. Be careful about drawing too many conclusions here. This is part political ideology, part personality and only a small part partisan politics.
The Marathon Bombing And Politics
NPR: How did the marathon bombing affect the races, if not the outcome?
Gray: It drained any remaining interest and press coverage of the race right out of the tank. There was basically a political news blackout for more than a week. Lynch seized on it to make the case that Markey was soft on terrorism, and it might have worked if Lynch had a few million to put behind that message in paid advertising. But he didn't, so it didn't stick. Ultimately, I think the bombings had no effect on the race other than sparing us a week of political ads.
Tolman: Barring any major slips or overreaches by the candidates, of which there were none, the bombing and shootout relegated virtually all other news to the back pages. The race was effectively put on hold for a week and when it returned it never regained what little momentum it had. With only two weeks to go, the front-runner, Ed Markey, was content to sit tight with his mound of cash and his lead. Lynch needed to change the dynamic and tried to do so, but lacked the resources to hammer it home to voters.
Since Scott Brown?
NPR: What has this primary season told you about the state of politics in Massachusetts, including how things have changed — or not — since Scott Brown won the special election to serve out the late Sen. Ted Kennedy's term just three years ago?
Gray: Even in a major league political state like Massachusetts, the voters and the political media get burned out. On the heels of the Brown-Warren Senate race and Mitt Romney being the GOP presidential nominee, this special election just hasn't captured anyone's interest.
Tolman: It is often said of Massachusetts that we take sports and politics very seriously. And we usually do. It is apparent, however, that we have grown tired of seemingly non-stop elections and a lot of voters have chosen not to tune in to this one, at least so far.