Three of the four hurdles to a Bernie Sanders presidency are obvious. They are: 1) securing the Democratic nomination; 2) winning the election against Trump in an unfavorable economic climate; and 3) governing in our divided society and political system.

The final hurdle is the Constitution. This involves the separation of powers, a powerful Supreme Court, and federal decentralization.

Each hurdle also suggests a temptation inherent in populist politics, which Sanders represents on the left, as Trump does on the right.

Securing the Democratic nomination in 2020 is a tall order for any candidate who is an avowed socialist. In Iowa and New Hampshire, majority white states, there was significantly more support for the three so-called moderate candidates than for the two on the left. Yet Sanders tied for first in Iowa and won narrowly in New Hampshire, because of the number of candidates and the fairly equal distribution of votes among his more centrist opponents. The presence of African American voters in the primaries from here on may not change this picture in Sanders’s favor. But although it is still not the same as winning the upcoming big state primaries, with their rich delegate counts, he seems to have overcome this hurdle over the weekend in Nevada.

The populist temptation in responding to this first hurdle, if it remains serious, is to threaten to boycott the election if anyone else becomes the Democratic candidate, which is more likely to come as a response from Sanders’s followers than from the senator himself. Sanders could counteract this by announcing his enthusiastic support for the party’s candidate, as he did in 2016. Unfortunately, in the last TV debate, he seems to have succumbed to this very temptation by being the only candidate to object to the mandated delegate count at the Democratic convention, insisting that the nomination be awarded by plurality. There is an implication here that if he attains this plurality and loses he may charge that the nomination has been stolen, and refuse to support the candidate that emerges from the convention. Of course, Sanders has plenty of time to resist this temptation and return to the position he held in 2016 when it was Hillary Clinton who could have won the nomination with only a plurality.

The second and main hurdle for Sanders would then be defeating the right-wing populist incumbent, Donald Trump, in an economic environment that currently seems to favor incumbency. Trump has his own significant and proven potential for mass-mobilization. There are many people, some my friends, who believe that only a left populism can defeat the right-wing version. I reject this on normative grounds, but admit its empirical possibility. Thus, the second temptation in overcoming this hurdle is to outbid or “trump” Trump’s anti-elitism, anti-media demagogy, trade protectionism, and vague, incompatible, and unachievable promises.

Sanders is arguably a more charismatic political figure than Trump. More importantly, he has never been part of the oligarchy. Trump, on the other hand, is extremely vulnerable to his own tactics being used against him.

He has been in office and has not followed through on his populist promise to “drain the swamp.” Instead, he has given huge tax breaks that benefit economic elites rather than his most committed working-class supporters. He has done virtually nothing to reindustrialize the so-called “Rust Belt,” and he has attacked parts of the welfare state dear to many of his supporters. He can try to compensate with amplifying anti-immigrant demagoguery, but it is not clear how long that strategy can continue to work in a country where immigrants are an entirely artificial problem. A left economic populism piggy-backing on mild social democracy would arguably be an effective weapon here.

Nevertheless, Sanders should resist this second temptation by not resorting to populist demagoguery. Instead, he should opt for a balanced ticket with a more moderate candidate as running mate and accept a compromise platform. The general election is quite a different matter than the primaries.

If Sanders were to win the presidential election against Trump, then comes the third hurdle, one even greater than the others: governing. Socialists have traditionally distinguished between minimum and maximum programs, the so-called “day after” and the long term.

Even advancing just a minimum program, however, President Sanders would face troubles right away. As Barack Obama found out to his chagrin, bare majorities are not enough to easily enact a president’s program in the United States. We owe the failure of the public option in the Affordable Care Act to a divided government with only a bare Democratic majority. Even assuming a pragmatic turn by Sanders, as anticipated and advocated for by liberal Paul Krugman and democratic socialist Alexandra Ocasio-Cortez, there would not likely be a sufficient Democratic majority in the Senate to easily pass much of the minimum program he has proposed.

Of course, Sanders could just abandon the distinction between minimum and maximum, and continue to advocate for both together in a permanent reform campaign. In such a case, the federal government could come to a standstill, as it has with Trump.

This outcome, which I think is likely, would be politically disastrous for the Democrats, as it was for the Republicans in 2018.

Assuming, on the other hand, that Congress passed some part of the minimum program — say, a public option in health care insurance open to all rather than only low-income, disabled, and senior citizens — Sanders’s problems would not be over. The right-wing Supreme Court could declare not only an expansive reform but also the entire Affordable Care Act unconstitutional. Alternative taxation projects, like a wealth tax, heavy taxes on inheritances, and other progressive taxes could meet the same fate.

And this would bring Sanders to the fourth hurdle: the U.S. Constitution.

Although I believe that formal features such as the Electoral College and our system of appointing judges are undemocratic and increasingly obsolete, as are rules like the filibuster and the procedures for fixing court memberships and jurisdiction, the Constitution cannot be attacked in the midst of political deadlock without potentially causing a political crisis. Sanders’s rhetoric, and his call for a political revolution, seems to welcome and even encourage such a crisis, even if neither he nor any of his followers seem to have fully thought through the possible consequences. Both the formal Constitution and its legislative procedures should be revised, but only with sufficient bipartisan consensus.

Unfortunately, the populist temptation in the face of the fourth hurdle may be to utilize legislative procedures that can be passed by simple majorities – or to pass a program by executive order, as Trump has done. The filibuster could be abolished by a simple majority of the Senate as presidential candidate and legal scholar Elizabeth Warren suggests , although the appointment of federal judges that had been made filibuster-proof has already had very bad consequences for the legitimacy of the judiciary. Even more significantly, Sanders could revive Franklin Roosevelt’s failed court-packing scheme , which has been supported in this campaign by another candidate , Pete Buttigieg. While these changes would be formally constitutional, the result would be the de-legitimization of the Supreme Court, the most crucial support of the formal Constitution.

My point is not to predict that Sanders will succumb to any of the four populist temptations. Nevertheless, the four hurdles in his way are serious obstacles to the changes he proposes: each could put an end to his political project — and to his personal ambitions.

In the case of the first three hurdles, however, Sanders has alternatives. To become the candidate, he can choose a fair and loyally democratic (and Democratic) path even as he tries to defeat his opponents.

To win the general election, he could form a ticket and platform around viable programs based on plausible estimates of the cost. Warren has shown this to be possible even while running on the left.

To govern successfully, Sanders would have to be ready to bargain and compromise with representatives of his party who are more gradualist or conservative, as well as with Republicans. He need not follow Obama’s path of bargaining with himself before facing centrist Democrats and Republicans, but he must be ready to accept negotiated solutions, which in some cases, like health insurance, may be better than what he himself proposed.

Finally, to overcome potential constitutional roadblocks, Bernie Sanders would have to see constitutional and procedural change as the work not of simple majorities, but of significant consensus throughout the political field.

As for the Supreme Court’s predictable resistance, a new Democratic president could count on one new appointment, whose identity and ability to persuade could be crucial, and could rally public opinion to try to induce “a switch in time,” as was the key to Franklin Roosevelt’s eventual overcoming of judicial sabotage.

Sanders may not be open to this kind of advice. But here is where his supporters and other Democratic and anti-Trump voters and pundits bear a heavy responsibility. We must oppose the populist option at each stage, and we must not at any cost reinforce the candidate’s own possible populist inclinations.

Above all, we should avoid the appeal to “revolutionary” options that exist only in the minds of sectarians but not in this real place, the complex and divided United States of America.

Andrew Arato is the Dorothy Hirshon Professor of Political and Social Theory at The New School for Social Research, and is the author of Adventures of the Constituent Power (Cambridge, 2017). You can visit his website here.