U.S. Senator Bernie Sanders is on a winning streak, having won eight of the last nine contests. Though Sanders still trails in terms of pledged delegates (whose support is tied to electoral outcomes in caucuses and primaries) by a count of 1,287 to 1,037, his deficit among superdelegates is even larger.

Created in the early 1980s to empower "party leaders and elected officials" (PLEOs), superdelegates can vote for whichever candidate they prefer at the presidential nominating convention. Among the approximately 712 superdelegates who will be traveling to Philadelphia in July, Clinton has support from 469, compared to 31 who have stated their support for Sanders.

Yet these figures reflect only the delegate count among contests that have already occurred: many superdelegates in future contests have already stated their preference for one of the two candidates. In Pennsylvania, for instance, which holds its primary on April 26, 18 of the state's 21 superdelegates have already announced their support for Clinton, with the other three delegates remaining publicly uncommitted. The Sanders campaign anticipates that it has support from as many as 38 superdelegates thus far.

Despite his lack of support among superdelegates, Sanders insists that there is still a "path to victory." While this victory will depend primarily on winning a majority of the 4,051 total pledged delegates, the Sanders campaign – citing its recent momentum and Sanders' purported strength against Trump in the general election – is also hoping to "flip" superdelegates that have thus far supported Clinton.

In Vermont, for instance, which has 10 superdelegates, Sanders supporters are lobbying four pro-Clinton superdelegates to back Sanders based on his overwhelming victory in the state's primary, which Sanders won with 86 percent of the vote. One Clinton superdelegate, former Vermont Governor Howard Dean, defended his persistent support for Clinton by claiming that superdelegates do not "represent people" because they are "not elected by anyone."

Sanders may have more luck among superdelegates in Wisconsin, where he won 57 percent of the vote in the primary on April 5. Sanders has support from one superdelegate thus far, state Rep. David Bowen, with more possibly to come. One of the six pro-Clinton superdelegates from Wisconsin, Christine Bremer Muggli, recently stated that she anticipates that most of her colleagues will be flexible and ensure, come July, that their support reflects the popular will of the party.

"I believe that if there was some way that Bernie Sanders was able to get more pledged delegates through elections in the primary," Muggli told Wisconsin Public Radio, "the superdelegates will follow that and bring together the party so that we can win."

Yet the 2008 Democratic primary contest shows that Sanders cannot expect to rely too heavily on winning over pro-Clinton superdelegates.

While Obama succeeded in securing the nomination after eventually overcoming Clinton's early lead among superdelegates, Obama's growth in superdelegate support derived largely from his victories in successive primaries and caucuses rather than from converting superdelegates from earlier contests.

In all, Obama "flipped" approximately just 30 pro-Clinton superdelegates before she dropped out of the race in June 2008. (It was Clinton's decline in support from superdelegates that led her in May 2008 to complain that there were "a couple of problems" with the party's primary process, including the role of superdelegates.)

In other words, if Sanders is to accrue more superdelegates, he will have to rely on winning over the non-committed by securing more victories in future contests. This strategy has yielded gains in Minnesota, where Sanders won the state's caucuses on March 1 and recently earned the support of a third superdelegate there, Rep. Rick Nolan, joining Minnesota U.S. Reps. Keith Ellison and Collin Peterson.

In the end, the Democratic nominee is likely to be decided by voters in the form of pledged delegates, who will comprise 85 percent of the delegation at the Philadelphia convention. With more than 40 percent of the pledged delegates remaining up for grabs, the Democratic primary is still very much a contested one.

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