WASHINGTON (MarketWatch) — The mainstream media is misleading the public by adopting a “fuzzy math” in treating the delegate counts for the Democratic nominating convention as carved in stone.

Given its bias against Donald Trump, the media are happy to parrot the Republican establishment’s prediction that their convention in Cleveland will be an “open convention” — that is, open to manipulation by the apparatchiks and the rules they set.

By the same token, given its pronounced bias in favor of Hillary Clinton, the media gladly repeat the spin of the Clinton campaign and the Democratic establishment by portraying that party’s contest as essentially over.

Not only compromised television anchors like MSNBC’s Chris Matthews, whose wife is drawing support from various Clintonites in her bid for a congressional seat in Maryland, are implying that the Democratic frontrunner’s lead in delegates is insurmountable. As a rule, pundits and even print reporters glibly adopt the inevitability spin.

Opinion Journal: Clinton and Sanders Battle

So when campaign strategists for Bernie Sanders hint at a contested convention, the Clinton campaign is quick to tweet “delusional,” and the press is happy to fall in line.

Even the redoubtable Nate Silver, whose FiveThirtyEight team so brilliantly charted Barack Obama’s electoral victories in 2008 and 2012, has gone along with the presumptions and polls that make a Clinton nomination all but certain.

Even so, Silver and his team have enough sense to leave the superdelegates out of the equation for the present.

Having set a target of how many delegates the two candidates must get in each primary to reach the 2,026 needed for a majority of pledged delegates, the FiveThirtyEight tracking currently has Clinton at 107% of her target and Sanders at 93%.

However, Sanders has met or exceeded his targets in seven of the last eight contests, while Clinton has fallen short six out of eight, so the momentum suggests Sanders will continue to narrow that gap.

The delegate math that considers Clinton the inevitable winner, then, is based on the presumption that the 469 superdelegates — elected officials and party leaders — who have previously declared their support for Clinton will in fact vote for her.

Yes, they may, but the fact is they are not “bound” in the same way pledged delegates in the primary contests are. They can change their minds at will.

The objective of Sanders campaign is to create sufficient political pressure for them to do so in large numbers.

The strategy depends on Clinton not winning enough pledged delegates in the primaries to clinch the nomination before the convention.

Even though Clinton currently has a lead of 211 among pledged delegates, 1,301 to 1,089 for Sanders, she would need to win more than 60% of the remaining primary delegates to reach the 2,383 needed to clinch the nomination, according to Slate’s Josh Vorhees.

That’s a steep hill to climb for a candidate who has lost seven of the last eight primary contests. If Sanders can win or keep the margins narrow in the big-state contests of New York, Pennsylvania and California, he will certainly succeed in keeping Clinton from clinching the nomination with pledged delegates.

Then the choice at the convention in Philadelphia comes down to the superdelegates.

There is little reason at present to presume they would abandon their support for Clinton but any number of things could change their minds between now and July — a Sanders victory in New York or another big state, further damaging news on the FBI’s investigation of Clinton’s email practices, a major gaffe or embarrassing video by the frontrunner, among others.

For the sake of argument, a graphic in Thursday’s Wall Street Journal showed that if superdelegates switched their endorsements in proportion to how their states voted, Sanders’s deficit would shrink to 19 (202 for Clinton vs. 183 for Sanders) from the current lopsided 438 (469 vs. 31). Note there are 712 superdelegates altogether.

Of course, if Clinton is ahead in pledged delegates at the convention and superdelegates were to vote in the same proportion, the former secretary of state would get the nomination.

But the superdelegates are there precisely to use their seasoned judgment about which candidate in a contested primary is better suited to win the general election.

Clearly the Democratic establishment at least for now feels that would be Clinton.

But if Sanders continues to win primaries, rack up delegates, raise tens of millions of dollars a month in campaign contributions, draw massive crowds to his rallies, and score double-digit leads against Clinton in demographics the party needs to win the general election — they will have to ask themselves some hard questions if the final count is close.

Who will lead the Democratic Party in the general election is a political question, not a mathematical one. If Sanders’s momentum continues to grow, the superdelegates would ignore that fact at their peril.