I honestly expect a fairly paltry showing from him once the primaries start. Last time his support included progressives, but was also sucking up nearly 100% of the "Anyone but Hillary" vote. Those people have other options this time. I also suspect that, with Bernie actually seeming competitive this time around, his opponents won't throw the kind of softballs that Hillary did (because she was mathematically a lock by Super Tuesday and didn't want to alienate his supporters). Things like his rape essay, his statements of support for Maduro's predecessor in Venezuela, a long history of foreign policy gaffs and some of his more ridiculous economic polcies are all going to be hitting him full force.

He's also a lot weaker now because he's pretty much the only Democrat who can't hammer Trump on his economic and foreign policy stupidity. Trade wars which alienate American allies, the changes to NAFTA, the botched withdrawal from Syria and so on, which are otherwise fair game for Democrats, are all unavailable to Sanders because he is both a protectionist and an isolationist and has a long history supporting both. He's virtually unable to touch Trump on an area which could absolutely hammer Trump's popularity, especially as the effects of tariffs are likely to continue to grow over the next couple years.