(CNN) - Republican Sen. Scott Brown kicked off his re-election bid Thursday in hopes of keeping the seat he won in the closely-watched Massachusetts special election in 2010.
He's now expected to run in another tight race, this time against likely opponent and Democratic frontrunner Elizabeth Warren, who's already proved to be a strong challenger in recent polls.
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"A lot has changed in these two years," Brown said at Mechanics Hall in Worcester. "It is not the establishment's seat. It is not the Democrats' seat. It is still the people's seat – it's your seat. For anyone running, it still has to be earned."
While Brown's campaign officially began Thursday, the Senate race has been well underway for months, as both Brown and Warren have raised considerable amounts of cash for their campaign war chests.
Warren, a Harvard law professor and former adviser to President Barack Obama during the development of the Consumer Financial Protection Bureau, jumped into the race in September.
During his remarks Thursday, Brown said Warren would be a divisive figure in Washington.
"She talks about how she's a, quote, 'rock thrower,' and rather than compromise she prefers to leave 'blood and teeth' on the floor," Brown said. "That sure doesn't sound like the kind of compromise and progress this country needs right now. I'm a bridge builder, not a rock thrower."
While Brown paints himself as a "compromiser," Warren is shaping her campaign as the one fighting for the middle class.
John Walsh, Massachusetts Democratic Party chairman, said that message will go a long with way with voters in the Bay State.
"I don't think Elizabeth Warren would ever be recognized as Wall Street's favorite. I think that will be key to the results," Walsh told CNN.
But the two candidates took an unusual step this week, each pledging to combat third party advertising-a popular force in the 2012 election cycle thus far, including the Massachusetts senate race.
A major player includes the so-called super PAC, an outside group allowed to raise and spend unlimited amounts of money on a candidate as long as it doesn't coordinate with the campaign.
As for the terms of their agreement, however, Brown and Warren remain divided.
Brown proposed that if any outside group spends money on ads that either bolster their candidacies or attack their opponents, then the candidate's campaign will self-impose a "steep financial penalty" and donate to charity an amount equal to half that spent by the outside group.
"No gimmicks, no fine print, no legalese," Brown said in a letter to Warren on Wednesday. "The people of Massachusetts deserve a Senate campaign in which they hear about their candidate from the candidates themselves, not through 30 second attacks ads funded by special interests and shadowy third party groups."
Warren responded later that night and requested that the two campaigns meet in person to discuss the terms of the arrangement, saying a private meeting would be "far more effective than negotiating through the media."
"When they meet, I hope they can go beyond your proposal," Warren said in a letter to the senator.
Because campaigns are legally not allowed to coordinate with super PACS, asking the outside groups to comply with the rules would be prohibited.
In her letter, Warren added the agreement should include a promise from both campaigns to reach out to broadcast outlets in the region, asking them to avoid airing the ads.
"We appreciate the spirit of your letter and proposal and look forward to discussing this further, and importantly, to reaching an agreement," she said.
Brown's announcement Thursday marked the two-year anniversary of his surprise election victory over Democratic candidate Martha Coakley. Brown filled the seat vacated by the late-Sen. Ted Kennedy.
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Go Elizabeth Warren. Our President needs intelligent, forward-thinking people like you supporting him in Washington after he is re-elected.
Question is, will the big money that bought, er backed Brown in the previous election come through again? They are, after all funding the romney campaign, can they afford another? It's obvious that Elizabeth Warren is a definite threat to them, I suspect they'll go all out. Warren is the better candidate, but Brown in their perfect stooge.
They'll find a way around it. My guess is special interests will form a Superpac for the candidate they oppose and air weak, but negative ads aimed at their own candidate in order to drain each others campaign funds.
It's like owning a business. While you're figuring ways to stop people from ripping you off, those very people are looking for new ways to steal from you.
I think Scott Brown has been doing pretty good job and has a pretty decent independent approach, but due to the rampant craziness of the republican party I would much rather have Elizabeth Warren in his seat. We need someone in congress to look out for the little guy.
Republican Sen. Scott Brown ,Your going to have have to work for it this time .
this is a key win for the republicans
The Wall Street "Favorite Senator" goes to his pretty–boy.
good luck...with those crazy MA voters...I'd move if I were you.
This time brown is on his own! Should run as a dem. and be honest about his views.
I hope you lose.
Go Ms. Warren!
He's done,so is Walker,Haley,Christie and the rest of the Repub corporate puppets.The teabaggin darlings that were going to save their party,what a joke...The middle class has seen thru their smoke screen,not for the people,only for corporate greed,Koch brothers and others take notice,your time manipulating the system is coming to an end....The Supreme Court will change and so will corporate influence,say hi to new Gov Warren..Her first job is to take out the Repub trash....Good luck Mrs Warren.....
"Brown proposed that if any outside group spends money on ads that either bolster their candidacies or attack their opponents, then the candidate's campaign will self-impose a "steep financial penalty" and donate to charity an amount equal to half that spent by the outside group."
Really? That is about one of the dumbest things that I have ever heard in my life. Sen. Brown must think Elizabeth Warren is a complete idiot to suggest something like that. What a sucker punch below the belt! Check this out.
Suppose a "Brown" superPAC decides to spend money on an ad that attacks Brown. That means the Warren campaign would incur a "penalty" from their coffers. But, suppose the "attack ad" is soft. Suppose there is a lot of money spent on this soft "attack ad." Now the Warren campaign must cough up bucks. You could drain your opponent's war chest if your superPAC runs enough "attack ads" against your self.
Which is the bigger fool? The one who suggested it, or the one who would agree to it?
Since Brown has not been a good little DittoHead Borg drone, and actually voted against his own party on some items, he is officially a RINO. What are the republicans in MA to do?
Warren will win by landslide. The country is watching this election.
Brown is TOAST. I hope Warren wins.
Congrats! He is my Senator and I will vote for him in a heartbeat over liberal Warren.
Brown is likely to be outspent by 3:1 this election cycle, and he's ~10 points behind in the polls already.
This is a stunt to get positive publicity. If Warren agrees to the proposal as stipulated, the best play would be to invest money into a Super-PAC supporting the opponent and funding very clumsy/tacky negative ads about you... Something like "Warren looks ugly without makeup" or suchthelike.
Mr. Brown should go back in his truck and become a model again. Elisabeth Warren is about 100 times more
intelligent and will win by a landslide.
Warren needs to lose in a spectacular fashion so that she has no confusion about what just happened.
Brown is the intelligent one in this race. Warren is in a fantasy land shared by Obama, unicorns and flying pigs.
Warren is a magnificant leader and public servant. You go girl!
Go Elizabeth. You have this election in the bag.
one of the good guys....
Elizabeth Warren for President in 2016. The intelligent and well-informed voters of Massachussetts will beat the money of Sen. Brown. I am from NJ.