Presidential hopeful Bernie SandersBernard (Bernie) SandersSchumer: Franken should resign Franken resignation could upend Minnesota races Avalanche of Democratic senators say Franken should resign MORE, the Independent senator and self-described democratic socialist, says that now in his heart he considers himself a Democrat. 
"Of course I am a Democrat and running for the Democratic nomination," Sanders told a New Hampshire town hall on Wednesday night. 
CNN host Anderson Cooper, the moderator of the town hall, had asked Sanders about a tweet from Sen. Barbara BoxerBarbara Levy BoxerBarbara Boxer recounts harassment on Capitol Hill: ‘The entire audience started laughing’ 100 years of the Blue Slip courtesy Four more lawmakers say they’ve been sexually harassed by colleagues in Congress MORE (D-Calif.), who attacked Sanders as an occasional Democrat.
Responding to Sanders's comment that Democratic front-runner Hillary ClintonHillary Diane Rodham ClintonGrassley blasts Democrats over unwillingness to probe Clinton GOP lawmakers cite new allegations of political bias in FBI Top intel Dem: Trump Jr. refused to answer questions about Trump Tower discussions with father MORE was a progressive on "some days," Boxer, a Clinton ally, tweeted, "Hillary is a progressive EVERY day. Bernie is a Democrat 'some days.'" 
After quoting Boxer, Cooper asked Sanders, "In your heart, are you a Democrat?"
"Sure," Sanders replied, citing his long tenure in the House and Senate Democratic caucuses, albeit as an Independent.
He went on to say that Clinton cannot claim to be both a moderate and a progressive.
"You can't go and say you're a moderate on one day and be a progressive on the other day.
"Some of my best friends are moderates. I love moderates. But you can't be a moderate and a progressive. They are different."
Sanders tried to play down expectations that he would secure a strong victory in New Hampshire, given he is currently ahead by almost 20 percentage points in the latest RealClearPolitics average.
"Of course we’re an underdog," Sanders said. "We are taking on the most powerful political organization in the country and that’s the Clinton organization."