RICHMOND — A potential coup is afoot among Democrats in the Virginia House of Delegates, where one Northern Virginia lawmaker who is unhappy with leadership is trying to line up votes to unseat his party’s No. 2 in the chamber.

Del. Scott A. Surovell (D-Fairfax) has been asking fellow Democrats if they would support him in a challenge to Del. Mark D. Sickles (D-Fairfax), the Democratic caucus chairman, according to two people familiar with his efforts.

A challenge could come as early as Saturday morning, when the party’s 32-member caucus meets privately in the Capitol before the House convenes for the final day of the 60-day General Assembly session.

But Surovell was still trying to line up votes late this week and was not sure he was ready to make his move, according to the two, who spoke on condition of anonymity in order to discuss a sensitive internal party matter.

Surovell and Sickles did not respond to messages seeking comment.

The power struggle comes at a time when most internal party squabbles in Virginia have taken place across the aisle, in the fractured GOP. But Democrats are already split over Gov. Terry McAuliffe’s pick for state party chairman. A leadership fight has the potential to further fracture the party in the midst of what could be a protracted budget standoff over Medicaid expansion.

Some Democrats who favor a leadership change have counseled Surovell to hold off until the Medicaid fight is behind them, while others suggested there was no time to waste if he wanted to start recruiting candidates who could help the party pick up seats in 2015 House elections, the two people said.

Surovell has been arguing that a change in leadership is needed because the party failed to make gains in last year’s elections, even as three Democrats swept statewide offices for governor, lieutenant governor and attorney general, the two said.

Surovell also has contended that Sickles will not have the time to devote to his duties as chairman because he is running to succeed retiring Rep. James P. Moran Jr. (D), the two people said. Surovell has also suggested that as caucus chairman, Sickles would enjoy an unfair advantage over the three other delegates in that race, the two said.

Sickles and Surovell have been on opposite sides of the party’s divide over McAuliffe’s nomination of Richmond Mayor Dwight Jones (D) for Democratic Party chairman, but their differences predate that controversy, which only erupted over the past week.

Some Democrats, including Sickles, oppose Jones because he has not supported gay marriage. Sickles recently announced that he is gay. Surovell, though a vocal gay marriage backer, has said the party should not have a “litmus test” on the subject.