Newton mayor Setti Warren, whose US Senate campaign has been short on cash and eclipsed by the emergence of Elizabeth Warren, plans to announce tomorrow that he is dropping out, according to an early supporter who received a phone call this afternoon.

A source close to the campaign confirmed the mayor was speaking with supporters and said he will make an announcement on the future of his Senate campaign in the morning.

Setti Warren was initially seen as a potential front-runner. He had worked for US Senator John Kerry and made an impressive initial run for public office in winning Newtons top job in 2009.

But many in Newton questioned whether he was running too soon after being elected mayor. And he had trouble raising money.

As of the most recent campaign finance filing deadline, at the end of June, his campaign was in debt.

The next campaign deadline is Friday and political insiders were eager to see if he could recover.

Elizabeth Warren, meanwhile, has stolen the spotlight since she entered the race this month, capturing attention from the Democratic establishment figures Setti Warren had been courting.

Meanwhile, other members of the Democratic field have said they intend to stay in the race in hopes of facing off against Republican Scott Brown. They include Alan Khazei, Tom Conroy, Bob Massie, Marissa DeFranco, and Herb Robinson.

Check back for updates.

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