Editor's Note: (Republican Charlie Dent is a former US congressman from Pennsylvania who served as chairman of the House Ethics Committee from 2015 until 2016. The views expressed in this commentary are his own. View more opinion at CNN.)

(CNN) The presidential primary system remains an impediment to political progress. It's hard to imagine a worse system to nominate candidates to the highest office in the land. If you think this system works well and need further evidence, look no further than the unfolding train wreck of the Democratic presidential primary.

In this volatile primary race, Bernie Sanders, a candidate leading in the national polls among a plurality of Democratic voters, may be poised to garner an insurmountable delegate lead, provided he doesn't stumble badly Saturday in South Carolina and next week's all-important Super Tuesday.

Charlie Dent

But as Sanders surges ahead, 2020 for Democrats looks a lot like 2016 did for Republicans. And it will yield a similar result: nominating an unacceptable candidate that so many smart people thought could never win a general election, let alone a major party primary contest. In today's politics, never say what will never happen because it may actually happen. Hey, can you say President Donald Trump?

The bottom line is that the Democratic primary will deliver a contest that many Americans may fear most in 2020: Trump versus Sanders. Both represent two sides of the same coin. They both appeal to anger. They scream that the system is rigged, you're a victim, and that they can give you your country back if only you follow them. At least, that's their tale.

Trump's appeal to anger is culturally based, blaming Mexicans, Muslims, the Chinese, s--t-hole countries (Trump has denied making this remark) and others for America's problems. That anger manifests itself in a wall that the President claimed would be paid for by Mexico, indiscriminate travel bans, naked protectionism marked by punitive tariffs, and daily assaults on decency. On the flip side, Sanders appeals to an anger that is economically based. For Sanders, it's the banks, Wall Street, big oil, pharmaceutical manufacturers, insurance companies, CEOs, the 1 percenters, the rich, and plenty of others he deems as enemies.

A choice between a know-nothing nativist and unapologetic "democratic socialist" — from the old school — is really no choice at all for a broad swath of the American public. It's akin to Mutually Assured Destruction (MAD) — a military strategy developed during the Cold War in which opposing sides use the threat of full-scale nuclear war, resulting in destruction of both sides. Since most Americans abhor suicide pacts, there will be a clamor for an acceptable alternative, or more aptly, a third way. (This is not a reference to the center-left Third Way think tank that recently released a powerful memo articulating the potentially devastating consequences of a Sanders nomination.)

Former Vice President Joe Biden is likely to win in South Carolina based on polling, and then perhaps can reshape the race going into Super Tuesday. But don't place any bets on it derailing Sanders. The remaining center-left candidates — Mike Bloomberg, Pete Buttigieg and Amy Klobuchar — will not consolidate around one candidate to stop the Sanders progressive juggernaut. Each of the moderate Democratic alternatives to Sanders believes he or she is the only viable alternative to Sanders, and that reality will prevent any one of them from launching a united front against Sanders. If Sanders commands a strong plurality in delegates short of a simple majority going into the convention, don't expect the feckless Democratic National Committee to deny him the nomination at the convention.

Despite the tribal and situational nature of modern American politics, many Americans seem to fall somewhere between the center-left to center-right of the political spectrum.

If a viable third alternative fails to emerge, these people may cast protest votes for people not actually running, or will simply refuse to vote for anyone at the top of the ticket — and they may do so in record numbers.

These voters want a candidate who believes in capitalism, reasonably regulated market-based solutions to problems, social tolerance and acceptance, and constructive international engagement that embraces America's global leadership role while supporting allies and stiff-arming adversaries. Most of all they'll want someone who conducts himself or herself in a thoughtful, deliberate and measured way. They want stability, not chaos and recklessness. Stated another way, they don't want a demagogue or fanatic, just a reasonably normal human being. The political center of the country desperately wants to vote for a candidate who can reassure them that America is not descending into an unrecognizable political and constitutional abyss.

Is this too much to ask? And why is our system seemingly incapable of producing this kind of alternative leadership at this moment?

An independent or third-party candidacy faces all sorts of impediments in our system. Ballot access restrictions, lack of political infrastructure and money are the most obvious and daunting obstacles to a successful independent candidacy. Finding a third alternative may be an impossible exercise, but if Bernie Sanders prevails in the Democratic primary, a third way may be the only way to rescue us from the unimaginable choice that awaits us.