Sanders is highly competitive in the first two states, Iowa (where he’s only narrowly behind Clinton) and New Hampshire (where he leads her). However, those states are favorable for Sanders demographically, with Democratic turnout dominated by Sanders’s base of white liberal voters. The question is whether Sanders can expand his coalition into more diverse states that will vote later on and where African-Americans, Hispanics and white moderates make up a larger share of the electorate. He won’t need to win every voter in these groups, but he’ll need enough of them to go from the roughly one-third of Democratic voters he captures in national polls now to the 50-percent-plus he’ll need eventually.
But Sanders would have an avalanche of momentum going for him after wins in Iowa and New Hampshire. The national press corps, which spins even minor stories into crises for Clinton, would portray Clinton’s campaign as being in a meltdown. Momentum usually matters in the primaries — and sometimes it matters a lot — but exactly how many Democrats would change their votes as a result is hard to say. The wave of negative coverage might be especially bad for Clinton, but it’s also possible that, because the media has sounded false alarms on Clinton before, she’d be relatively immune to the effects of another round of bad press. One factor helping Sanders: Voters who had been attracted to his message before, but who weren’t sure he could win, would mostly have their doubts removed after he beat Clinton twice.
[W]hatever happens in Iowa, we can already reach this conclusion: Democrats, and Hillary Clinton, will have to engage in a serious, genuine effort to learn from the Sanders phenomenon and what it really represents. ...
going forward, don’t underestimate what Sanders represents. The Sanders phenomenon raises possible warning signs for Clinton’s chances in a general election. His ability to engage, excite and involve younger voters — his ability to make them feel invested in politics — throws into sharp relief Clinton’s relative failure, at least for now, to do the same. Some Dem pollsters, such as Stan Greenberg, have already begun warning that Clinton will have to make extra efforts to excite millennials.
Sanders has figured out a way to speak to a sense that the system is fundamentally broken in very profound ways that put our future in doubt. Those two things may be related: Sanders appears to make young voters feel they have a stake in his candidacy — and by extension, in this election — because they think their future is the one that’s in doubt. By speaking in bold strokes about the need for gargantuan solutions, he seems to makes their deep concerns about the future feel heard and, perhaps, assuaged. (While Donald Trump’s diagnosis of the problem is very different, leading him to wallow endlessly in demagoguery and xenophobia, he also has flummoxed pundits who under-appreciate his ability to speak effectively to a similar sense that people feel the system is fundamentally failing them.)