Like Trump, Sanders comes from outside the institutional party he seeks to lead, and a substantial portion of his appeal rests precisely on that independence, and on pent up frustration with the party leadership. Like Trump, Sanders is leading a movement deeply bound up with his own persona, something hard to imagine sustaining itself in his absence. And like Trump, were Sanders to achieve victory, he could face persistent resistance within the party to promoting his agenda, and he would certainly have difficulty staffing his administration with people associated with his movement rather than the institutional party. That’s a fact that will surely affect the actual course of policymaking in a Sanders administration as it has in Trump’s.

But there are two crucial differences between Sanders and Trump. First, Sanders is a sincere ideologue like Goldwater and Reagan, not an opportunist. He is running to transform his party ideologically rather than simply conquer it and make it his plaything. There’s a reason why Trump has done so little to actually turn the GOP into a worker’s party and to repudiate the wealth-favoring policies backed by its donors: Because he is not actually that interested in policy. Sanders is.

That difference cuts both ways, however. It makes it easier for Sanders to get between Trump and his lies, and separate him from that portion of his supporters who believed he was a relative moderate in 2016. But it also makes it easier for Trump to retain the loyalty of his party’s regulars, and to separate Sanders from the portion of his coalition that is worried about him not because he might lose but because he might win. Cynicism has its advantages as well as its drawbacks.

But another difference is even more important. Trump took over a party that absolutely despised its leadership.