A Facebook post and tweet — "Defranco for congress" — set rumors swirling earlier Wednesday that the onetime candidate would jump in the race. Asked whether the social media post indicated she had in fact made up her mind, DeFranco only repeated that she's looking at the race.

Tierney already has one primary challenger in Seth Moulton, a former Marine and first-time candidate who announced his plans to run on Tuesday.

Defranco launched an ill-fated challenge to party favorite and now Sen. Elizabeth WarrenElizabeth WarrenThe private alternative to the National Flood Insurance Program  Warren: 'I'd be very glad' for Sessions to quit Warren gives Trump an 'F' on draining the swamp MORE (D) in the Massachusetts Senate Democratic primary in 2012, but failed to garner enough delegate votes at the state party convention to land a spot on the ballot.

The immigration attorney ran to the left of Warren, a Democrat already known for her progressive values, and raised less than $50,000 for her campaign.

But Tierney is considered one of the most vulnerable incumbents heading into 2014.

He significantly underperformed President Obama and narrowly won reelection in 2012, suffering attacks focused on his family's engagement in an offshore gambling ring.

His opponent, Richard Tisei, an openly-gay former state lawmaker widely believed to be one of the strongest Republican recruits in the nation, is leaning towards a rematch in 2014.

DeFranco declined to assess what had changed between her 2012 run and now, but did indicate she feels Tierney would not be the strongest Democrat in a general election.

"2012 was a presidential year. Obama beat Mitt Romney in the state of Massachusetts by about 23 points. John Tierney beat his Republican opponent by 3,000 votes. 2014 is not a presidential year," she said.

Though a contested primary is likely to be a bruising, costly affair, DeFranco's run also has the potential to ease Tierney's path to the nomination by splitting the anti-Tierney vote with Moulton.