Democratic presidential candidate Sen. Bernie Sanders speaks to his campaign volunteers at the local headquarters in Bowling Green, Ky. Wednesday. (Austin Anthony /AP)

It may not matter what Bernie Sanders meant this week when he promised to push for a contested convention this summer.

Even with his victory in the Indiana primary Tuesday, it remains all but impossible for the senator from Vermont to win the nomination.

Sanders used the phrase at a news conference over the weekend at which he predicted that neither he nor Hillary Clinton would arrive at the Democratic National Convention in July with the 2,383 delegates needed to win the nomination outright.

Clinton was on track, even with her loss in Indiana, to secure a majority of pledged delegates. Sanders’s point was that the nominee would also need a hefty supply of superdelegates — the 718 party leaders and elected officials who are automatically granted a say at the convention — and that he planned to persuade these Democrats to support him.

That’s the part that didn’t grow any more likely on Tuesday. Already, 520 superdelegates have publicly said they support Clinton, 39 have said they support Sanders and 160 have not publicly announced their choice. Sanders’s argument on Sunday was that superdelegates should consider switching their allegiance to him — particularly those from states that he won.

Bernie Sanders won the Indiana Democratic Primary on May 3. Here's how. (Peter Stevenson/The Washington Post)

There’s little agreement with that sentiment among the superdelegates themselves. Rep. Sander M. Levin (Mich.), a superdelegate supporting Clinton, said he has spoken with many fellow superdelegates in recent weeks.

“The reality is that the overwhelming number who are committed to her did so because they think she’ll be the strongest president in these very challenging times,” he said.

Levin dismissed concerns that he’s bucking the will of his state by supporting Clinton even though Sanders won Michigan.

“It was a narrow victory. It was almost a split decision,” he said. “I think one needs to take that into account, but also one’s own experience. Mine told me that especially in these very challenging times that she would be the most effective president.”

Former Pennsylvania governor Ed Rendell, one of Clinton’s most vocal supporters, was even more resolute.

“Absolutely not,” he said of the possibility of superdelegates switching allegiances from Clinton. They will select whoever has won the most delegates “and that will surely be Secretary Clinton,” he said.

Sanders “has a right to contest every single primary on the calendar,” just as Clinton did in 2008, Rendell added. But he is still upset by the senator’s suggestion at the start of the primary season that superdelegates would play a minimal role in the nomination process. In the months since, Rendell said that Sanders supporters have targeted superdelegates with “vile emails and threatening emails.”

“You can’t trash us in February and then come back and tell us how much you love us in May or June or July,” he said. “Remember, Bernie’s spent two months beating the hell out of superdelegates. We remember that. We remember how unworthy we were in February.”

Several superdelegates supporting Sanders declined to comment, didn’t respond to requests for comment or passed along perfunctory statements of support. Others supported Sanders’s bid to win over superdelegates.

“If Senator Sanders is close or is actually leading by the time we get to the convention, I think he definitely has a case to make that in at least the states that he won, those superdelegates should be backing his campaign,” said Troy Jackson, the former state Senate majority leader in Maine.

James Zogby, a Sanders superdelegate from the District and the president of the D.C.-based Arab American Institute, said: “I just don’t think it’s possible — or among those who support him, desirable — for him to just walk away from this. And I don’t think this is something that [party leaders] can wrap their heads around, because they’re used to everyone falling into line.”

Tad Devine, Sanders’s chief strategist, said, “The contest between the two campaigns will be decided by those delegates who are free until the time they walk on the floor of the convention to support either candidate.”

“Things have changed since the campaign began,” Devine added. “People should take a look at that. The role of superdelegates is not to be the first voice but to be the last voice. If one candidate got a lot stronger, and one candidate got a lot weaker, that’s something they should think about.”

Devine acknowledged that it will be very difficult to persuade superdelegates to switch allegiances unless Sanders finishes on a very strong winning streak — something Sanders aides argue is possible after Tuesday’s victory in Indiana.

“Yes, we must stipulate that,” he said. “But I think we have a viable path.”

Even under the rosiest assumptions, Sanders would need a minimum of 159 superdelegates already publicly supporting Clinton to switch sides for him to win the nomination, according to a Washington Post analysis.

There are a total of 4,769 Democratic delegates — 4,051 pledged delegates allocated based on results in the states and 718 superdelegates, a few of whom get only half a vote. That special class of delegate includes every Democratic Congress member, governor and state party official, as well as prominent party members, including former presidents Jimmy Carter and Bill Clinton.

A Democratic candidate needs 2,383 delegates to clinch the party’s nomination. As of Wednesday, Clinton had 2,205 total delegates, compared with Sanders, who had 1,401, according to a tally by the Associated Press.

Sanders acknowledged Sunday that he would need to win 65 percent of the remaining delegates to match Clinton’s current pledged delegate lead. That figure actually grew a little Tuesday, to close to 66 percent, given Sanders’s relatively narrow win in Indiana. Based on polling in the remaining states, the target remains highly unlikely.

And even if Sanders were to catch Clinton, he would still need 358 superdelegates to support him. If he were to hold onto his 39 superdelegates and pick up the remaining 160 undecided votes, he would still need 159 delegates now supporting Clinton to clinch the nomination.

Some Sanders supporters expressed outrage that so many superdelegates appeared unwilling even to consider the possibility.

“I’m amazed that in some of these states the voters go 60 percent or 70 percent one way or the other and the superdelegates don’t flinch? I just can’t get over that,” said Jackson, the superdelegate from Maine. “Superdelegates should be reflecting the will of their own state, not what the establishment thinks.”

Dottie Deans, the chairwoman of the Vermont Democratic Party, is supporting Sanders as a superdelegate and in a statement credited him for “an exciting and inspiring campaign.”

“He has a desire to ensure that those voters feel like part of the process heading into July,” she said, adding that “the Democratic Party will come together in July and stand behind our nominee.”

Devine said he does not think continuing to contest the nomination will hurt the Democratic Party heading into the fall.

“We can do an awful lot of good things for the party between now and then,” he said, arguing that competitive contests in the upcoming states would increase voter registration and overall interest in the presidential race on the Democratic side.

“I’ve been in campaigns that have wanted it to end,” he said. “That doesn’t mean you’re better or stronger for it.”