Hillary Clinton attends a rally with Senator Bernie Sanders (I-VT) at Portsmouth High School Gymnasium in Portsmouth, New Hampshire on Tuesday, July 12, 2016. (Melina Mara/The Washington Post)

Bernie Sanders, having just successfully pushed to make the Democratic platform more liberal, said Friday that he is turning his attention to advocating for a series of electoral reforms, which he’ll fight for on the floor of the party’s convention this month in Philadelphia, if necessary.

Sanders, who endorsed Hillary Clinton this week, said in an interview that he’s now lobbying to reduce the number of superdelegates who have a say in the Democratic nomination and to open all primaries and caucuses to independent voters, among other changes.

“We have some serious concerns, and I expect some of those concerns may wind up on the floor of the convention,” said the senator from Vermont, who was the runner-up in the Democratic primaries.

Sanders and his allies first plan to present proposed changes to the rules committee that is meeting in advance of the July 25 start of the Democratic convention. If unsuccessful there, the next move would be to try to force a debate among all the convention delegates — a potentially contentious moment as Democratic leaders seek to unify the party.

Former Democratic rivals Hillary Clinton and Bernie Sanders spoke together at a Clinton campaign rally in Portsmouth, N.H. July 12. Here are key moments from their speeches. (Sarah Parnass/The Washington Post)

Former congressman Barney Frank (Mass.), a co-chairman of the convention’s rules committee, made no predictions Friday about the success of Sanders’s efforts but said that he expects robust debate over those and other matters when his panel convenes next Saturday.

The changes Sanders is pushing would have no effect on his race against Clinton, which he conceded Tuesday, but could have helped him had they had already been in place.

Clinton won more pledged delegates than Sanders in the primaries and caucuses, collecting 2,205 to his 1,846. But Clinton’s biggest advantage in the race was the number of Democratic leaders and other party insiders known as superdelegates who also have a say on the nomination and pledged to support her in Philadelphia.

According to the latest Associated Press tally, Clinton has the backing of 602 superdelegates to 48 for Sanders.

Sanders said many of those party elites pledged to support Clinton before he even got into the race, a dynamic he considers “totally absurd and undemocratic.”

Sanders said he does not necessarily think that all of the more than 700 superdelegates should be eliminated — there is a rationale for elected officials, he said — but he said he plans to present a proposal for reducing their influence on picking the party’s nominee.

Sen. Bernie Sanders, I-Vt. leaves a meeting hosted by Senate Democrats with Democratic presidential candidate Hillary Clinton on Capitol Hill in Washington, Thursday, July 14, 2016. (AP Photo/Evan Vucci) (Evan Vucci/AP)

Sanders said he will also push to open all Democratic nominating contests to independents as well as Democrats. In the states that currently allow broader participation, he tended to perform better.

“Democrats should be welcoming people into their processes, not keeping them out,” Sanders said.

The rules for state primaries and caucuses are set by state law or state parties, but Sanders said there are ways for the Democratic National Committee to “encourage and incentivize” states to make changes in their elections.

One option would be apportioning more delegates to states that follow DNC preferences.

Sanders said he also wants to push states that hold caucuses, as opposed to primaries, to expand the number of hours during which voters are able to participate. In many cases, a caucus is limited to several hours, and participants are required to stay for the entire time.

Sanders said that such rules are unfair to people whose jobs don’t allow them to attend.

Frank, a Clinton supporter during the primaries, said the more-democratic reform would be to replace caucuses with primaries. In Sanders’s race against Clinton, Sanders tended to perform better in caucuses, which typically have lower turnout than primaries.

Sanders’s push on electoral reforms follows several victories with the committee that updated the party’s platform. At Sanders’s urging, the committee adopted planks advocating a $15 an hour minimum wage and stepped-up measures to combat climate change.

Though Sanders fell short in some areas, including trade policy, he said he has no plans to push for additional changes to the platform at the convention.