As Bernie Sanders continues to win primaries, it becomes increasingly likely that he will be the Democratic presidential nominee. Of course, it isn’t yet inevitable that he’ll be the standard-bearer, as Joe Biden could conceivably use a strong showing in South Carolina to jump-start his campaign. For now, however, Sanders must be regarded as the front-runner.

This forces us to consider what Sanders’ prospects in the general election might be. I’ve long thought that he should be regarded as a wild card. It would not be surprising if we wake up on Nov. 4 and find that Sanders has won a large victory. It would also not be surprising to wake up and find that Trump has won comfortably. Here are three reasons Sanders could win, and three reasons he couldn’t.

There won’t be a “Never Sanders” movement. When James Carville went on his (first) rant against Bernie Sanders, most people focused on the former Clinton campaign manager bashing the rising populist candidate and saying that he was “scared to death” of him. What I noticed was his conclusion: “If Bernie is the nominee, I’ll vote for him. No question.”

This is important. George McGovern was doomed by a massive crossover vote of conservative Democrats who could not stomach the South Dakota liberal. But those Democrats have long since left the Democratic Party. With the exception of perhaps Joe Manchin and Collin Peterson, the Democratic members of Congress will almost certainly vote for Sanders, even if those in conservative districts keep him at arm’s length for their own electoral reasons.

Likewise, there won’t be a “Never Trump” analogue on the Democratic side. “Never Trump” Republicans were animated by a number of concerns. Some objected to his lack of bona fides on social issues; he won these voters over through his list of judges and the selection of Mike Pence as his running mate. Others were concerned about his stances on foreign and economic policy. Still others were concerned about his personal shortcomings.

In the end, “Never Trump” was a paper tiger: three upper-middle-class guys in a think tank cubicle, two of whom were voting for Gary Johnson anyway, as I half-joke. Trump overwhelmingly carried Republicans. Sanders won’t even have this problem to overcome. Going into November, the Democratic Party will likely be nervous, but it will be unified. This limits his downside.

Elections are referenda on the party in power. I have long been of the view that elections are fundamentally referenda on the party in power, and that electoral choices are something of a mirage. If the electorate likes the president, he wins. If they dislike him, he loses.

The simple truth is that Donald Trump has been an unpopular president, whose job approval has been net positive for exactly one day in the RealClearPolitics average. If this election is mostly about him, and things do not change for the better, voters will say “I don’t like Bernie Sanders, but my only alternative is Trump.”

Sanders avoids racial identity politics, and his class-based politics will resonate with Obama-Trump voters. Two weeks ago, when asked about spending in politics, Sanders said: “You know, people have a right to participate in the political process. But again, getting back to the fundamental issue, the reason we have so much income inequality, the reason we are the only major country on earth not to guarantee health care to all people, the reason that almost all new income and wealth goes to the top 1% is precisely because of a corrupt political system which allows billionaires to have inordinate influence of the economic and political life of the country.”

This might scare some Romney-Johnson voters back into the Republican fold, but for a much wider swath of the electorate this will resonate. While this group of voters also tends to like President Trump, Sanders’ message offers them a way to come around to the Democratic Party, to the extent the election really is a choice.

Moreover, Sanders' persona and message avoid the racial identity politics that often pushes these voters away from the Democratic Party. Although Pete Buttigieg is to Sanders’ right, I think Buttigieg would potentially have more of a problem because he codes as a Harvard-educated cultural liberal. For many voters, Sanders will code as the curmudgeonly eccentric uncle with whom you disagree at Thanksgiving but share a laugh with afterwards. He’ll be able to get some of these voters back. Relatedly, I’ve long thought that Trump’s heavy regional dialect and “unique” hair helped blue-collar white voters (who are often mocked for those attributes) relate to him; it may work the same for Sanders.

Remember, all Sanders has to do to win is hold the Clinton states and flip Pennsylvania, Wisconsin. and Michigan. That is not a Herculean task against an incumbent president with a job approval mired in the low-to-mid 40s.

Here, however, are some reasons why Sanders could have trouble:

Trump’s job approval is increasing. For much of the summer of 2017, the received wisdom was that Trump’s job approval had a ceiling of about 40%. Then, slowly, over the course of early 2018, his job approval began to climb (probably saving the Republican Senate in the process). People then declared a new ceiling of 45%, which he struggled to exceed throughout 2019.

Today his job approval stands at 46.3%, the highest of his presidency. His net job approval is negative 4.3%, the closest to positive it’s been since March of 2017. Barack Obama saw a similar rise in his job approval in early 2012 (after a lengthy period of having an upside-down job approval) that pushed him from a certain loser to an eventual winner.

Some of this might be the economic narrative taking hold, but some of it is probably that the referendum model is not 100% accurate. Yes, job approval and electoral choice are related, but at a certain point the direction of the causal arrow reverses for some. People decide that while they don’t like the president, after seeing the primary unfold on the other side, they can’t vote for those guys either. To resolve this cognitive dissonance, they convince themselves that the president isn’t so bad. This helps explain President Obama’s improved job approval in 2012, followed by a steady decline the following year; we saw a similar effect for President Bush in 2004.

Sanders simply alienates too many voters that Democrats need. Trump was effective in 2016 because the issues where he was perceived as extreme by the punditry -- immigration, trade, and political correctness -- resonated with voters who were weakly attached to the Democratic Party and accelerated their movement toward Republicans. He lost some suburbanites who were uncomfortable with his stance on these issues, but overall the tradeoff redounded to his benefit.

Sanders has the opposite problem. He’s problematic for groups that Democrats increasingly rely upon in order to win elections. In this sense, he’s similar to Elizabeth Warren. He appeals to core Democratic voters, but the upper-middle-class suburbanites will be uncomfortable with his tax increases, his move to abolish private health insurance, and his spending plans.

Cuban-Americans -- an important group in Florida who are gradually trending toward Democrats -- will dislike his praise of Fidel Castro. Many Gen Xers, who grew up during the Cold War, will find his kind words about the Soviet Union’s subway system and youth programs discomfiting. Voters in western Pennsylvania and eastern Ohio will find his fracking ban a problem. And so forth.

Many of these voters will ultimately justify a vote for Sanders based on their discomfort with the incumbent president. But many won’t. There’s thus a possibility that his electoral coalition suffers a death by a thousand cuts. There’s also the possibility that moderates, a group Democrats have held since the 1990s, will rebel against the socialist label, creating a blowout election. In other words, while Sanders only has to hold the Clinton states and flip Pennsylvania, Wisconsin. and Michigan, it’s not a foregone conclusion that he can hold all the Clinton states.

There is a difference between having a Republican attack ad run against you and running on a Republican attack ad. Of course, these charges have been lobbed against Democrats before, and they’ve managed to win nevertheless. That’s because the Democratic candidates have had plausible deniability in the past. Republicans would run an ad charging that the Democrat was a socialist, and the Democrat would respond with “don’t be ridiculous, I’m not a socialist.” Even liberal candidates like Obama could point out that their health care plans were based on keeping a private insurance system; Republicans were left arguing about what the ultimate endgame might be.

With Sanders, there is no such deniability. His reaction to the “socialist” accusation is “I’m a democratic socialist, and that is good.” His reaction to the “praised Castro” charge is “Castro got some things right.” His reaction to the charge that he wants to abolish private insurance, in a country where people generally like their insurance companies, is to argue that "Medicare for All" will be better.

The first approach is to deny the charge, on things where swing voters will likely be predisposed to disbelieve the charge. The second approach depends on convincing people that their previously held political beliefs about something are wrong. That is a much harder task.

Overall, I don’t know which set of arguments is better. It’s why Sanders could win big or lose big. Or, perhaps, the factors just cancel out, and we’re left with a close election where fundamentals dominate in a sharply polarized society.