The fight to replace Secretary of State John Kerry, which pits Rep. Ed Markey, D-Mass., and Republican businessman and former Navy SEAL Gabriel Gomez against each other, comes to a close tonight.
Short of a shocking surprise, it looks likely Markey will win, but here's what to watch for.
|Scott Brown Redux? Not Exactly|
There was excitement at the beginning of this race that for Republicans this would be Scott Brown redux.
Republicans were counting on the charismatic story behind Gomez, a 47-year-old, Harvard-educated, former Navy SEAL, successful businessman and second-generation Colombian immigrant who's running against the political establishment -- especially because he was taking on Markey, 66, a 37-year veteran of the U.S. House of Representatives at a time when Congress couldn't be hated more.
But, as polls showed Gomez consistently behind, it's become clearer that it's more likely Massachusetts will go back to having two Democratic senators, as might be expected in the blue state. Remember: Scott Brown may come from Massachusetts, but this is the same state that voted for President Obama by a margin of 23 points over native Bay Stater Mitt Romney.
A Boston Globe poll from last week showed Markey leading Gomez 54 percent to 41 percent.
Gomez wants to keep it as tight as possible, and it's not only because he would like to win, although he obviously wants that, too. Gomez wants to keep it within single digits so he's able to work on his political skills to add to his intriguing personal narrative and have a political future ahead of him.
There could also be Republican second-guessing over underwhelming financial support and Team Gomez "I told you sos" if Gomez is able to keep it within single digits.
Of course, aside from his intriguing personal story, Gomez is far from a perfect candidate. His temperament on the stump was called into question when he called his opponent "pond scum" for running an ad that pictured Gomez and Osama bin Laden.
The Markey ad hit Gomez for his association with a group that attacked President Obama for politicizing bin Laden's death.
|Outside GOP Cash Didn't Come|
Despite little help from outside GOP groups, the National Republican Senatorial Committee did send staff to help out on the ground, as well as hold fundraisers for Gomez. NRSC Chairman Jerry Moran, R-Kan., sent an e mail to donors this week saying they had spent nearly $1 million on the race.
However, Gomez's team was hoping for outside money to pour in, which didn't happen despite Gomez being the exact type of candidate Republicans said they wanted after the handwringing post-2012. Outside Republican groups have been notably silent even as Gomez has been outspent by Markey by at least $4 million.
Gomez's team wasn't afraid to speak out about being left in the lurch, telling ABC News' Rick Klein last week that national Republicans appeared to have grown too timid after the 2012 electoral wipeout. If they can't support a Latino entrepreneur and military veteran against a career politician, they asked, what are they waiting for?
"This is the world's longest psychotherapy session," Brad Todd, a top Gomez strategist said in an interview, referring to the GOP's post-election soul searching. "We've gotten awful comfortable on the couch. It's time to get up and get in the game.
"The evidence here is that Democrats are scared to lose, and Republicans are scared to win," he added.
|Obama Swings In|
Despite his lead throughout the race, Markey had big-name Democrats come campaign for him, including President Obama, first lady Michelle Obama, former President Bill Clinton and Vice President Joe Biden.
Some saw it as a sign of worry in the last weeks, despite his lead, and could show some concern for Democrats into the 2014 midterms. Democrats will be defending 21 of the 35 Senate seats on the ballot next year.
Of course, if Markey wins big this may all be forgotten and it could serve as an important psychological victory for Democrats and a return to normalcy in a blue state.
It wasn't just national Democrats who played a role in the campaign. Throughout the process, Markey was eager to compare Gomez to national Republicans, saying a vote for Gomez would be a vote against women's rights and a vote for Mitch McConnell and the GOP agenda.
Gomez mostly tried to distance himself from national Republicans, even saying on the trail, "I am fully aware that in a few months from now, some in the Republican Party will consider me to be a pain in the butt. And I am OK with that."
|Lines of Attack|
Among the lines of attack that stymied Gomez were whether he took advantage of a tax loophole improperly, although not illegally.
Markey also consistently hit Gomez, noting his policy stances on abortion and gun control. Gomez has said he is "personally pro-life," but won't attempt to change abortion law, calling Roe vs. Wade "settled law," in an interview with the Boston Globe.
He accepted exemptions like rape, incest or danger to the life of the mother, but none of that seemed to matter as ads and stump speeches aimed to paint Gomez as an extremist.
Gomez consistently said he would work across the aisle and President Obama, even writing an open letter to him "welcoming" him to Massachusetts when he campaigned for his opponent.
He said voters needed new leadership after 37 years of Markey in the House, consistently stressing that Markey lived in Maryland, not Massachusetts -- but the line of attack never really caught on.
Turnout will, of course, be an essential factor in the results tonight, and there has been evidence throughout the race that the Massachusetts electorate is fatigued and not engaged in a way it was during the 2012 match-up between Brown and Democrat Elizabeth Warren.
Voters have endured the 2010 special U.S. Senate election, the 2010 gubernatorial election, a 2012 U.S. Senate election and the 2012 presidential election.
As for how that could affect the final results, it's hard to tell, but both sides have been working on get-out-the-vote efforts, with Biden urging Democratic voters this weekend to make sure they cast their ballots.
"Look, folks, don't put yourself in a position where you get up Tuesday morning, and it's an incredibly low turnout, and you say, 'Good God, if I'd only gone down one more block, if I'd only made 20 more calls, if I'd only spent a little more energy, this wouldn't be the case," Biden said. "This is the first time, in my understanding, that you've ever had a vote for a major office in this state in the middle of June."
ABC News' Rick Klein and Michael Falcone contributed to this report. This story has been updated since it was first posted.