With early caucus and primary states holding delegate caucuses on Tuesday, at least five would-be candidates were already urging liberal Democrats to “take a vote” to support them at this month’s state political conventions.

“On the Democratic side in Iowa, Nebraska, South Carolina, North Carolina, and South Dakota, delegates are going to be selected and many are going to be superdelegates,” Vermont Senator Bernie Sanders said Tuesday afternoon, announcing that he had collected 110 signatures on petitions calling for party-level selection of Democratic state delegates.

California Senator Kamala Harris announced a petition drive of her own on Sunday, saying that candidates should pick up the “necessary signatures to ensure that everyone has the opportunity to speak up, to be heard, and to be represented.”

Oregon Democratic Senator Jeff Merkley sought delegates in Nevada on Monday, calling on caucus attendees to back candidates “as community leaders and leaders of your community.”

Candidates Kamala Harris, Bernie Sanders and Jeff Merkley urge delegates to support them at state conventions. (Photo: AP)

At this month’s party conventions, not only will voters choose delegates to all levels of the party, from the Legislature to the White House, but state parties also hold primary elections on March 3, when polling shows the most organized liberal activist groups also will be going to vote.

Mr. Sanders has built an organization to push Democrats to support his platform. His advisers said that a successful Indivisible, Indivisible Youth and Progressives United effort was boosting them in Iowa, but that they were understaffed and outspent compared to the remaining candidates.