A sticker is stuck on a resident's jacket after he cast his votes at a polling place in the District in 2012. (Eva Hambach/Agence France-Presse via Getty Images)

Norman J. Ornstein is a resident scholar at the American Enterprise Institute.

One of the most enduring themes in U.S. presidential politics is the fantasy of a knight in shining armor emerging to vanquish pretenders on both sides and lead the country to a world free from polarization, pandering and partisan manipulation. Actually, it is more a nightmare than a fantasy — and it is playing out this election cycle in ways that could be dangerous and deleterious.

With the presidential nominating race nearing its formal start, we learned recently that billionaire former New York mayor Michael Bloomberg commissioned a poll to test the waters for an independent candidacy. That follows an expression of interest from former senator (and failed Democratic candidate) Jim Webb, who suggested that he could pull together disaffected Republicans and Democrats with the multitude of independents in the middle. At the same time, a group of leaders from politics, business and academia is pushing to force the Commission on Presidential Debates to include an independent in the general-election debates this fall.

With a Republican race that has Donald Trump and Sen. Ted Cruz (Tex.) outdistancing their many rivals and a Democratic one in which Hillary Clinton still hasn’t found a clear path past Sen. Bernie Sanders (I-Vt.), plus surveys suggesting growth in the number of self-identified independents, it may not be surprising that there is again interest in an independent candidacy. After all, in 1992, a year marked by populist uprisings on the left (Ralph Nader), right (Pat Buchanan) and center (Ross Perot) and a clear lack of enthusiasm for either Democratic nominee Bill Clinton or Republican President George H.W. Bush, Perot led in the polls at least five months before the election. And even after imploding, he won 19 percent of the vote.

The fantasy of the independent savior did not go away with Perot. Led by investor Peter Ackerman, the group Americans Elect in 2012 sought to use the Web to nominate an independent candidate through a competitive process; the effort collapsed, but Ackerman is among those pushing to add a candidate to the fall debates.

Why is a significant independent presidential candidacy both a fantasy and a nightmare? First, consider the actual landscape of partisan identity in the United States. It is true that Gallup recently found a record number of independents in the electorate — an astonishing, 42 percent. But it is also true, as The Post’s Philip Bump pointed out, that a great deal of research shows that most self-identified independents lean to one of the two major parties — and behave politically in a fashion that is almost identical to the behavior of stronger partisans. That means, among other things, that the increasing phenomenon of straight-ticket voting affects the lion’s share of independents just as it does self-identified Democrats and Republicans. And it means that the number of genuine independents is small.

That alone does not mean that an independent, under the right conditions, would have little or no support. Emory University’s Alan Abramowitz and Steven Webster have shown that partisans in recent years have not so much increased their attachment to their own party as developed stronger antipathy to the opposite one. So at least theoretically, a strong independent candidate might attract some partisans on both sides who believe he or she has a better chance than their own party’s candidate to thwart the evil candidate from the hated other party.

But what would that mean in practice? For an independent candidate, at best, it would mean three candidates splitting the popular vote, probably roughly a third apiece, with the independent edging out the others with perhaps 35 percent. But that would mean little for the outcome. Presidential contests are decided by electoral votes. An independent might well secure some electoral votes, but in such a race, no candidate would come close to the majority of 270 required, under the Constitution, for victory.

What then? The Constitution says that if no candidate gets a majority of electoral votes, the election moves to the House of Representatives, among the top three electoral vote-getters. There is a twist: House members do not vote individually but by state, a majority of which are required to select the president. Currently, 33 states have House delegations that are majority-Republican; three are evenly split; and Democrats control 14. There are no independents — zero, nada — in the House. The numbers, of course, could change in the fall elections, but the chances of having any states controlled by independents, indeed of having any independents at all in the House, are close to nil. And given the margins of control in most states, the dominance of majority-Republican delegations isn’t likely to change.

The states themselves would have to caucus individually to determine how their votes would be cast. Members might vote for the winner of the popular vote, or the winner of the vote in their own districts, or the winner of the vote in their states, or based on partisan loyalty. Multiple ballots could be required. But the odds would be great that, in the end, the House would choose the candidate whose party controlled the most delegations.

Whatever the outcome — an independent ultimately elected president but without a single lawmaker with any attachment to him or her; or a partisan, probably a Republican, chosen primarily because of the partisan tilt of gerrymandered districts — it would not be healthy for the country. A president elected this way would limp into office lacking legitimacy via a process ripe for logrolling and corrupt bargaining. (Read the history of the 1824 election, for example.)

There are reasons to despair over the trajectory of our presidential election process, and of our political process more generally. That trajectory would not be positively altered by a prominent independent candidate parachuting into the 2016 presidential race or being force-fed into the fall debates.