(CNN) Vermont Independent Sen. Bernie Sanders never actually joined the Democratic Party -- and some party officials are still bothered by it.

Bob Mulholland, a Democratic National Committeeman from California, introduced a resolution that the party will consider at its Las Vegas meeting later this week calling on Sanders and Maine Independent Sen. Angus King -- both of whom caucus with the Democrats -- to actually join the party.

"There's only two real teams in the presidential election in 2020, and that's Trump versus a Democrat," Mulholland said Tuesday night. "And with Trump running the White House, we need more people to call themselves Democrats and stop standing on the sidelines."

Any DNC member can introduce a resolution -- and Mulholland's has a long way to go before having the party's endorsement. It'll head to a resolutions committee that will meet Friday in Las Vegas, where it could be amended, rejected or approved. It would then advance to the full DNC membership for a vote Saturday.

Even then, it would have no binding impact on Sanders and King.

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