The Democratic National Committee voted Friday to change its rules and bar anyone from running for the party’s 2020 presidential nomination without being a Democrat at the time of announcing one’s candidacy.

In 2016, Sen. Bernie Sanders (I., Vt.) ran an unexpectedly competitive primary campaign against Hillary Clinton despite being an independent, and the DNC’s rules and bylaws committee appears to have this in mind with the new rule, Yahoo News reports. Sanders’ supporters are interpreting the move as a sign of spite.

"We just came off a devastating presidential loss in 2016. It would seem to me the actual impetus would be to expand the Democratic party. I just for the life of me don’t see any motivation for this beyond personal spite," said Mark Longabaugh, who was a senior adviser to Sanders’ 2016 presidential campaign.

Sanders is an independent who has identified as a democratic socialist and caucuses with the Democratic Party in the Senate. His 2016 presidential campaign claimed he would become a Democrat "for life," but he ultimately decided not to join up, remaining an independent in the Senate.

The rule may not affect Sanders himself if he does decide to run in 2020, however. He has typically chosen to run for the Democratic Party’s nomination in Vermont Senate races to fend off Democratic opponents and then has declined the Democratic nomination, running in the general election as an independent. The Vermont Democratic Party has supported this strategy and ruled he enjoys the "rights and privileges" of a party member.

But the decision is still a move toward exclusivity in the party, which is a criticism Sanders’ supports have trumpeted on the party's newly formed Unity Reform Commission.

"I don’t have any worries that Bernie Sanders could meet the criteria to run as a Democrat in 2020, but it always puzzles me that there are some Democrats who want to do this and promote this," Longabaugh said. "I scratch my head and ask why they would want to make the party more narrow and more exclusive."

Sanders’ former campaign manager said the Democratic Party should not be excluding the "millions" on the left who aren’t in the party.

"Do they really want Bernie and millions outside the party?" Sanders' 2016 presidential campaign manager Jeff Weaver said.

On Saturday, the last day of the rules and bylaws committee meeting, members will vote on whether to keep superdelegates, the unpledged delegates in the primary that Sanders and his supporters said favored the establishment. The pro-Sanders faction of the Unity Reform Commission have demanded superdelegates be eliminated from the process, and some think that is now more likely given the new requirement for party membership.

Maria Cardona, a party operative who previously worked for Clinton, said the requirement had unanimous support.

"The entire committee backed this. It was unanimous," Cardona said. "It was done to ensure that the presidential nominee of the Democratic Party is actually a Democrat."

Sanders is running for re-election in Vermont this year. He is expected to win the Aug. 14 Democratic primary by a wide margin.