This commentary originally appeared on The Hill.
While President Trump no longer brags about his polling numbers, poll after poll, going back to early 2016, decisively prove that Sen. Bernie Sanders (I-Vt.) towers above Trump in public support and remains the most popular political leader in America.
If one does a google search for "Sanders most popular," the result will be a long list of news stories about polling that demonstrates the phenomenon of public support for Sanders.
If one does a web search for "Trump most unpopular," the result will explain why so many Senate Republicans are beginning to run away from Trump faster than an Olympic sprinter as the 2018 midterm elections come closer.
The most important political question in America as the 2018 election season begins to heat up is why Sanders towers over other national political leaders in public support. In my view, there are two fundamental reasons for the phenomenon.
The first reason is that the progressive populist agenda championed by Sanders offers the most appealing options for the future of the nation. This is the most underestimated factor in political discussion in all political media. Most of the political debates on cable and network television tend to pit Democrats embedded in the Democratic establishment against Republicans embedded in the Republican establishment and Trump-style, alt-right Republicans, whose views are out of touch with mainstream American opinion.
The second reason Sanders is the most popular political leader in America is that he embodies authenticity, integrity and a political discourse based on ideas he deeply believes in, which many Americans share. Voters know where Bernie Sanders stands, and they like that. His phenomenal popularity brings together his personal credibility with voters and his progressive agenda that voters who approve of him share.
Every day, the Sanders-affiliated group, Our Revolution, motivates far more enthusiasm and support for progressive Democrats and causes than the sclerotic Democratic National Committee.
Why does the media pay so much deference to the "Trump base," which constitutes approximately 35 percent of voters, while paying so little respect to the much larger base of voters who favor Sanders and his agenda?
Republicans and some of the more corporatist Democrats falsely charge that Sanders is "too far left." If Sanders is too far left, why is he the most popular political leader in America? Why did the Real Clear Politics summary of polling in 2016 consistently show Sanders defeating Trump by landslide margins of 10 percent or more?
When Sanders condemns greed on Wall Street, he speaks for huge numbers of Americans. When Trump condemned greed on Wall Street, then surrounded himself as president with the very kinds of people he condemned, he committed a fraud against his base and against all voters. This accounts, in part, for his disastrous weakness in polling.
When Sanders champions single-payer healthcare, he is taking a position supported by liberals and conservatives throughout the democratic world and by large numbers of American voters. Contrast that with the various GOP healthcare plans that have been unmitigated political disasters for Republicans.
The problem is not that Sanders is too far left, but that our political discourse has shifted too far right.
When Sanders supports a tuition-free public college education for young people, when he calls for aggressive action to combat climate change, when he champions civil rights and human rights for all Americans and when he calls for Medicare for all, he is speaking for far more voters than Trump and Republicans.
The issue is not which candidate to support in 2020, but what direction the Democratic Party should follow to bring about the post-Trump era that is in the early stages of forming today.
Democrats are not fundamentally divided about the issues Sanders champions, many of which were included in the party's 2016 platform that was supported by Hillary Clinton and her supporters.
In many ways, Sanders today is like Teddy Roosevelt in the 1912 presidential campaign when he led the progressive Bull Moose party. TR did not win that election, but his platform in 1912 became the foundation for the great and historic changes ultimately enacted under the leadership of Woodrow Wilson, Franklin Delano Roosevelt, Harry Truman, John F. Kennedy and Lyndon Johnson.
Sanders is winning the battle of ideas. The most popular political leader in America is setting the stage, as TR did in 1912, for the next great Democratic president — whoever he or she may be — to be elected in 2020.
Commentary by Brent Budowsky, a columnist at The Hill. Budowsky was an aide to former Sen. Lloyd Bentsen (D-Texas) and former Chief Deputy Majority Whip Bill Alexander (D-Ark.). He holds an LL.M. degree in international financial law from the London School of Economics.
For more insight from CNBC contributors, follow @CNBCopinion on Twitter.