Speculation over the 2020 US presidential elections has already gotten contentious. The Democratic field looks as if it’s going to be crowded, and new prospects are floated by the press seemingly every week, from Oprah Winfrey to Beto O’Rourke. With just under two years to go until election day, it’s best not to become too consumed by presidential speculation. But for those on the left who want to defeat Donald Trump and advance egalitarian political values, it’s important to start to think about who can succeed. For those of us who believe in radically transformative political change, the choice is already clear – Bernie Sanders is the only viable option.

Based on his record, Sanders should be the progressive favorite by default. In 2016, he ran an impressive insurgent campaign that came close to defeating the party elite’s handpicked candidate. Savvier Democrats have already recognized that Sander’s message is the one that best suits the mood of the electorate.

His ideas have set the agenda for the Democratic party for the past two years, with elected officials trying to burnish their progressive credentials by doing photo ops with Sanders and adopting his policies, from free college to Medicare for All (a plan that even the majority of Republican voters now favor). Many polls suggest he is the most popular politician in the country, and would be the clear favorite in a match-up against Trump. Attempts to portray Sanders as the candidate of white “Bernie Bros” ignore the facts – Sanders has higher favorability ratings among people of color than any other Democratic politician. It’s obvious that he’s the party’s best shot. He has a formidable team of experienced organizers, national popularity and name recognition, and a clear, bold agenda that can win over working-class people of all genders and races.

What about the other frontrunners? Some current polls put Joe Biden ahead of Sanders in a potential primary. But while Biden’s “Uncle Joe” persona has endeared him to Democrats across the country, no serious progressive can support him. For one thing, Biden has declared himself indifferent to the concerns of millennial voters, saying he has “no empathy” for young people who complain about student debt, precarious employment, and high rent. I don’t know about other millennials, but I prefer a candidate who can empathize with me.

Biden has also spent a long career in Washington failing to take important stands at critical points. He has misrepresented his pandering to racists during the 1970s, and his handling of Anita Hill’s testimony during 1991’s was infamously shameful. (After decades in which Hill waited for an apology from Biden, he finally gave a partial one this year, while still declining to accept blame for what happened to Hill.) If that wasn’t enough, Biden’s creepy history of routinely violating women’s personal space should make his candidacy a non-starter in the post-#MeToo era.

How about Beto O’Rourke, the “Kennedyesque” golden boy currently being floated as a potential nominee? O’Rourke turned in an impressive showing against Ted Cruz in Texas. But O’Rourke is a member of the centrist New Democrat coalition, and his commitment to progressive values is so lukewarm that he refuses to even use the word “progressive” to describe himself. His record as a legislator is thin, and he has been noncommittal and evasive when discussing core progressive policies like tuition-free college and single-payer healthcare. Since he hasn’t taken the lead on pushing a left agenda in Congress, there’s little reason to think he would be effective at doing so as president.

In fact, every candidate other than Sanders has qualities that should be deeply troubling to those on the left. Elizabeth Warren, whose calls for a more democratic economy put her closer to Sanders than any other senator, has called herself a “capitalist to my bones” – a sharp contrast with the democratic socialism with which the majority of millennials sympathize. (Warren’s disastrous handling of the “Native American” controversy also does not suggest the kind of nimble political instincts crucial to taking on a master of sleaze and scandal like Donald Trump.)

Kamala Harris has a record of overseeing and then defending serious prosecutorial misconduct as California’s attorney general, and racial justice advocates strongly criticized her for her failure to hold police accountable. Cory Booker, whose political rise was fueled by corporate money, has such warm feelings for Wall Street that he actually criticized Barack Obama for being too harsh on private equity firms.

Kirsten Gillibrand spent the first part of her career as a lawyer for Big Tobacco, and according to the American Conservative was originally elected by “running to the right”, such as by staunchly opposing drivers’ licenses for undocumented people. Gillibrand has recently begun to sound far more progressive, but someone who served as the paid agent for “merchants of death” faces a high burden to prove they’ve changed.

A candidate should be judged on their record. Based on how recently most of the 2020 prospects have embraced the progressive agenda, it’s reasonable to suspect some opportunism. Sanders, on the other hand, has a lifelong history as a thorn in the side of the establishment. Even as a teenager, Sanders was getting himself arrested in civil rights demonstrations.

As mayor of Burlington, he pioneered an innovative community land trust approach to affordable housing. He has been an efficient legislator, even earning the title “amendment king” for his success in getting measures through Congress. And he has shown a willingness to take principled stands, including his early opposition to the Iraq war plus his votes against the Defense of Marriage Act and the Patriot Act.

There are only a few serious criticisms of Sanders, the main one being “he’s too old.’ But while age might be a more serious factor if the current president were far younger, Trump is a septuagenarian like Sanders. Sanders still shoots hoops, he criss-crosses the country giving speeches, and he has more energy than many of us who are less than half his age. If Trump tries to make an issue of Sanders’ superior age, experience, and wisdom, Sanders can just challenge him to settle it on the basketball court.

There are a few other criticisms that can be made of Sanders, including his unfair criticism of leftist “open borders” advocates. He has cast bad votes (the 1994 Clinton crime bill comes to mind) and sometimes makes frustrating gaffes. I do not think Sanders is the ideal candidate, the one I would make in a laboratory. It would indeed be nice to have someone younger, ideally a woman of color (if only the constitution didn’t bar Alexandria Ocasio-Cortez!) But the question isn’t “Is Sanders flawless?” Rather, it’s “Is Sanders the best candidate we have available?” To that, the answer is clear. No other 2020 prospect comes close.

• Nathan Robinson is the editor of Current Affairs