Transcript for Massachusetts Race Could Decide Who Controls the Senate
So, ohio could decide who wins the white house, but another race under way in massachusetts could decide which party will control the senate. Tonight, two fierce competitors with a lot of money pouring in. Abc's jonathan karl has more. Reporter: It's an epic battle. Elizabeth warren, the relentless liberal crusader who took on wall street against scott brown, the republican with a pickup truck who won a near miraculous victory two years ago and is finding out how hard it is for a republican to win again in massachusetts. You have a little dent in this thing. What happened? Being a republican, you get dented around a little bit. Reporter: Brown is a moderate, but warren portrays him as a tool of fat cat republicans. The vision can be boiled down to this. "I got mine. The rest of you are on your own." Reporter: Warren has electrified progressives with her unapologeticliberalism. Well, this is class warfare, this is whatever. No. There is nobody in this country who got rich on their own. Nobody. Reporter: Brown says warren would be just another hyper partisan senator and is an arrogant harvard professor to boot. Excuse me, I'm not a student in your classroom. Please let me respond. Reporter: Brown tripes to hard to be independent, he often takes on his own party's leadership, including mitch McCONNELL. Do you think you'll support mitch McConnell? I've already let him know that I'mdy gusted by everything that's going on and he's going to have to earn my vote. Reporter: Disgusted by what? The grid lock. Total grid lock down there. Reporter: But as warren reminds voters, this race is about more than scott brown. People all around the country understand that this race may be for control of the united states senate. Reporter: In fact, democrats believe if they can defeat scott brown, they are virtually guaranteed to keep control of the senate. And, diane, they're probably right. And from capitol hill tonight, jonathan karl, thank you, jon.
This transcript has been automatically generated and may not be 100% accurate.