The following article by Ruy Teixeira, author of The Optimistic Leftist and other works of political analysis, is cross-posted from his blog:

Bernie-mentum.

There’s no doubt that it’s here, as a spate of polls confirm. Not that Sanders is the front-runner overall, as the chart from 538 below shows. But he has definitely improved his position significantly, even as Warren’s has radically declined. This is obviously excellent news for the Sanders campaign on the cusp of the Iowa caucuses with the New Hampshire primary right behind.

So Sanders looks more like a plausible nominee than he ever has before in this campaign. But could he beat Trump?

Of course he could in the weak sense that it’s possible, given that Trump is so unpopular and that Democrats seems so motivated. But is it likely?

That’s the big question. The Sanders campaign and most of his supporters would naturally answer this in the affirmative. Their theory of the case, as far as I can make it out, is pretty simple. Bernie will so energize potential Democratic voters that any losses he might incur among swing or moderate voters will be drowned under a tsunami of Democratic turnout. Indeed, Sanders generally argues that this is the only way the Democrats can win the election; a more moderate candidate will fail to generate this turnout and will lose.

Maybe. But then again, maybe not. Sanders will, after all, have a lot of liabilities to overcome. They are well-summarized by Jonathan Chait in a blistering polemic on the New York magazine site:

“Sanders has gleefully discarded the party’s conventional wisdom that it has to pick and choose where to push public opinion leftward, adopting a comprehensive left-wing agenda, some of which is popular, and some of which is decidedly not. Positions in the latter category include replacing all private health insurance with a government plan, banning fracking, letting prisoners vote, decriminalizing the border, giving free health care to undocumented immigrants, and eliminating ICE…

Sanders combines unpopular program specifics in the unpopular packaging of “socialism.” The socialist label has grown less unpopular, a trend that has attracted so much media attention that many people have gotten the impression “socialism” is actually popular, which is absolutely not the case.

Compounding those vulnerabilities is a long history of radical associations. Sanders campaigned for the Socialist Workers’ Party and praised communist regimes. Obviously, Republicans call every Democratic nominee a “socialist.” But it’s one thing to have the label thrown at you by the opposition, another for it to be embraced willingly, and yet another thing altogether to have a web of creepy associations that make it child’s play for the opposition to paint your program as radical and dangerous. Viewing these attacks in isolation, and asking whether voters will care about Bernie’s views on the Cold War, misses the way they will be used as a stand-in to discredit his entire worldview. Nobody “cared” how Michael Dukakis looked in a tank, and probably not many voters cared about Mitt Romney’s dismissive remarks about the 47 percent, but both reinforced larger attack narratives. Vintage video of Bernie palling around with Soviet communists will make for an almost insultingly easy way for Republicans to communicate the idea that his plans to expand government are radical.”

It’s hard to believe that these liabilities won’t cost Sanders a significant number of votes from more persuadable voters toward the middle of the political spectrum. So it all comes down to whether Bernie and his brand of politics really can produce the bonanza of votes he promises from an “energized” progressive electorate.

Again, could be, but I have my doubts. I’ll detail them with an empirically-based (naturally) analysis in a future post.