Independent Vermont Sen. Bernie Sanders can’t have it both ways and seek the Democratic Party presidential nomination without officially being a Democrat, according to the Democratic National Committee (DNC).

Sanders will be expected to sign an attestation from the DNC that he is a Democrat, the Washington Examiner reported Thursday.

The DNC is planning to brief presidential candidates in the next few days about what to expect as the nomination campaign gains steam. That interview happens every election cycle but this year there reportedly will be a “candidate affirmation form” included in the binder. (RELATED: Hillary Alumni Swipe At Bernie As He Launches 2020 Campaign)

“Candidates who have officially announced their candidacy will have a week to return a signed copy of the affirmation form to the DNC,” the official told the Examiner. “As any additional candidates enter the race, they will be provided with the same information and will be required to return the form in the same time frame.”

The addition comes as a result of reforms that followed criticism that the 2016 nomination was completely controlled by party bosses. The winner of that contest, former Secretary of State Hillary Clinton, appeared to be an establishment favorite.

Under the new rule, the candidate has to “be a bona fide Democrat” who has not said or done anything in public life that would be contrary to the “interests, welfare, and success” of the party. A candidate has to attest to that commitment in writing, promising to run and potentially serve as a Democratic member. (RELATED: Bernie Sanders, Climate Hawk, Spends Nearly 300K On Private Jet Travel In A Month)

The DNC isn’t saying if they have a contingency plan for anyone who refuses to sign.

Sanders, who ran a campaign in 2016 that nearly upset front-runner Clinton, is the early leader in an ever-growing pack of Democratic candidates. After declaring his candidacy for 2020 on Tuesday, Sanders picked up $1 million in donations within an hour and almost $6 million after 24 hours. He has already received the support of Democratic Vermont Sen. Patrick Leahy and Democratic Vermont Rep. Pete Welch.

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