Sen. Bernie Sanders (I-Vt.) speaks during a keynote session at the South by Southwest conference in Austin on March 9. (David Paul Morris/Bloomberg News)

THE UNEXPECTED outcome of the 2016 presidential election has put Democrats and other left-of-center people of goodwill in a uniquely opportune position. They have the chance to reimagine what the character of mainstream-left politics will be in the United States, and to articulate those principles anew to a populace that appears to be listening. But what to imagine, and what to say?

As The Post’s James Hohmann recently reported, the center-left Third Way think tank has proposed that, in the words of Senior Vice President for Policy Jim Kessler, “Democrats need a positive, modern, forward-looking economic agenda that gives people hope that they’re going to have the opportunity to earn a good life in the future.” But Kessler also “noted that while the Bernie Sanders wing of the Democratic Party is focused on income inequality, Third Way has decided to focus on the concentration of opportunities.” In other words, the mainstream left has a decision to make: focus on inequality or focus on opportunity?

But, speaking as a member of the “Bernie Sanders wing,” I don’t actually view the two focal points — opportunity and inequality — as fully separable. The impact of inequality on the overall economy and political climate means that, unless inequality itself is reduced, individual initiative won’t have much impact and conditions for ordinary people in America will continue, in key ways, to worsen.

Sanders himself agrees. “You have an economic situation where a tiny number of people have enormous amounts of wealth,” Sanders told me at his Senate office Wednesday morning, “and politically, you have the Koch brothers and a handful of billionaires buying elections.” Sanders pointed out that the top 1 percent of earners would rake in roughly 83 percent of the benefits of President Trump’s tax cuts, a series of policies for which Koch-led groups spent more than $20 million. As Yale University political scientist Jacob Hacker pointed out in The Post, the decision to supply a generous tax cut to the rich — greatly encouraged by the vast wealth of billionaire donors — is a de facto decision to reduce expenditures that help ordinary Americans, “like public investments in infrastructure, education, research and development, and the regulation of labor and financial markets.” Put simply, inequality allows the wealthiest Americans to exert undue control over politics, thereby maintaining the conditions that made them rich in the first place, and hamstringing government efforts that could increase opportunities for the rest of us.

And inequality weakens the economy itself. Economic researchers have argued that American inequality worsened and prolonged the negative effects of the Great Recession and that continued inequality has left less well-off families more vulnerable to economic shocks going forward, meaning that future crises might unfold even more disastrously than the last.

Most important, rising inequality can swamp the gains that broadening opportunity is supposed to deliver. A recent study by Harvard University researcher Robert Manduca found that, while the median black family had risen from the 25th percentile of the overall income distribution in 1968 to the 35th percentile in 2016, and closed the black-white gap in income rank by about 28 percent, the concurrent rise in overall inequality was so dramatic that it completely negated the black gains. The ratio between black and white income, in other words, remained unchanged: As the distribution of income skews ever more toward top of the spectrum, succeeding in climbing up from the bottom doesn’t amount to much.

According to recent Pew survey data, about 62 percent of Americans think our economic system unfairly favors the rich and powerful, with the sentiment strongest among millennials, who have grown up in the wreckage of the Great Recession. Fully 82 percent of Americans, likewise, think inequality is either a very or moderately big problem — and again, millennials are the most likely to identify it as a very big problem. The old guard may be more skeptical, but the young vanguard of the American left is convinced: Inequality is “a very serious issue,” in Sanders’s parlance.

So it makes sense to treat inequality as a problem in and of itself — which is what Sanders is doing, or trying to do. On Monday, Sanders will host a televised town hall focused strictly on inequality, which is an important start. But Democrats who tend to prefer an opportunity-first approach over an inequality-first approach should still tune in: As Yale historian Samuel Moyn recently observed, even the robust tradition of human rights is less effective and less imaginative due to the corrosive impact of inequality. If Democrats want to formulate a bold, enduring political vision that will speak to the future that Americans want for themselves, they need to accept that opportunity is a result and companion of equality, not a separate choice altogether.