Washington (CNN)Sen. Bernie Sanders is a political independent, who proudly calls himself a socialist. As he declared his presidential candidacy Thursday, he pledged to run on the Democratic ticket.
Potential roadblock for Bernie Sanders rises in New Hampshire
He could hit an early roadblock in New Hampshire -- not with Hillary Clinton, but William Gardner, who has guarded the state's first-in-the-nation presidential primary for four decades as Secretary of State. He said he isn't sure whether Sanders meets the state's requirement to be on the presidential ballot.
"If they're going to run in the primary, they have to be a registered member of the party," Gardner told CNN. "Our declaration of candidacy form that they have to fill out says 'I am a registered member of the party.'"
Gardner, who takes pride in personally greeting all presidential candidates in the fall when they file their paperwork at the State Capitol in downtown Concord, N.H., stopped short of saying Sanders would be excluded from the 2016 Democratic primary ballot. But he said he did not know how Sanders could answer the simple question on the form: Are you a registered Republican or Democrat?
"We have only two legal parties in New Hampshire," Gardner said in an interview. "The primary is only for those legal parties."
For months, as Sanders has flirted with announcing a presidential candidacy, his aides have said he would not have trouble getting on the ballot. He meets the guidelines of the Democratic National Committee, which only requires candidates to have "demonstrated a commitment to the goals and objectives of the Democratic Party."
Even if Sanders wanted to formally declare his allegiance to the Democratic Party, which he has not done during a quarter-century in Congress, he would technically be hamstrung. Vermont, his home state, is one of more than 20 across the country that does not register voters by party.
But even though Sanders meets the Democratic National Committee rules, access to presidential ballots are also determined by a patchwork set of state-by-state election laws. The Iowa caucuses, which will kick off the presidential race next year, do not require candidates to formally declare their party registration. Caucuses are run by the state party, not dependent upon state election law.
Tad Devine, a Democratic consultant to Sanders, said Sanders would have to "pledge some allegiance to the Democratic Party."
"He won't have to sign on to every plank of the Democratic platform in order to get in, but he will have to acknowledge that he is running as a Democrat," Devine said. "I think Bernie will have to do that."
Sanders has caucused with the Democratic Party ever since he came to Washington as a congressman in 1991. He unsuccessfully ran for the United States Senate in 1971 as a member of Liberty Union party. In 1981, when he successfully ran for mayor of Burlington, Vt., he did so as an independent.
It's unlikely that any Democratic candidate would challenge Sanders right to run on the party's ticket, Gardner is known to be a stickler for rules. In a telephone interview on Wednesday, he read the form aloud and said he didn't see any wiggle room for presidential candidates who were technically not registered Democrats or Republicans.
But when reminded that Howard Dean, the former Vermont governor who sought the Democratic presidential nomination in 2004, qualified for the New Hampshire ballot, even though he was also not a registered Democrat, Gardner paused for several moments. He said he would dig out Dean's paperwork from storage and check.