Bernie Sanders: Sanders seems to be surging, but the reality check looms: Even if he sweeps the first three states, he is likely to get trounced in South Carolina and will have a difficult time in other Southern states. He could sweep Super Tuesday in the North and win California, perhaps with an assist from Bloomberg, but still find himself trailing in delegates.

More importantly, he is likely to face a full-throated attack from the Democratic establishment and (perhaps more importantly) center-left media outlets if he looks to be on track to become the nominee. He was treated with relative kid gloves by Hillary Clinton in 2016, but if he is a genuine contender, many Democrats will work tirelessly to defeat him, or at least to throw the election to the convention. This dynamic would have mattered more 20 years ago, when the party and media had stronger gatekeeping functions, but it will still matter.