Months ago, I wrote a commentary asking “Can Bernie Sanders beat expectations?” He has surged in the polls since then, prompting pundits to dub this the “summer of Sanders.” So the question now is: Can Bernie Sanders beat Hillary Clinton?

Most political analysts say he has no real chance; arguing, in effect, that the political deck is stacked against him. They contend he can’t raise enough money; he is too little known; and as a self-described “democratic socialist,” he can’t appeal to many non-progressive voters.

James Pindell, an astute reporter for The Boston Globe, explained that “voters’ summer flings with candidates typically don’t last” -- in past election cycles there have been such surges by other anti-establishment candidates, only to lose to better-funded, more “mainstream” pols.

But to conclude that little-known upstarts never beat the odds would be ignoring nominees like George McGovern, Jimmy Carter and Barack Obama.

Sanders is sometimes compared to Eugene McCarthy who, in 1968, did better than expected in the New Hampshire primary against President Lyndon Johnson. That led to Robert F. Kennedy entering the race, and LBJ announcing that he would not seek reelection. McCarthy and Kennedy split the anti-Vietnam War vote during the primaries, and after RFK's assassination, Vice President Hubert Humphrey, the establishment candidate, won. But what would have happened if Kennedy had not entered the race, and it was only a two-man contest between McCarthy and Humphrey? We’ll never know, so the argument that Sanders is another McCarthy doesn’t really apply if the Vermont senator is able to keep his status as the only Democrat who can compete with the establishment candidate, Hillary Clinton.

Sen. Bernie Sanders, I-Vt., speaks at the Alliance for Retired Americans 2015 National Legislative Conference in Washington in July. (Molly Riley/AP)

The Clinton camp now admits to being worried about the Sanders threat. They fear that he could beat her in the Iowa caucuses. The New York Times reported that Clinton advisers were surprised by the Sanders surge:

“Mr. Sanders’ rising fortunes pose a bind for the Clinton team," the Times reported. "Directly challenging the senator on his policies and record could elevate his candidacy, alienate some liberal Democrats and make Mrs. Clinton look anxious. Yet continuing the current strategy — vigorously courting voters while hoping they conclude that Mr. Sanders is unelectable — requires Mrs. Clinton to put faith in an Iowa electorate that snubbed her seven years ago, choosing Mr. Obama and Mr. (John) Edwards over her.”

In New Hampshire, Sanders has been so encouraged by polls and crowds that he predicts he’ll win his neighboring state. Indeed, he now predicts, “We’re going to win Iowa, New Hampshire, the nomination and the presidency.”

Many surging candidates make the mistake of believing that their momentum is unstoppable — but then they make a gaffe, or some economic or military development suddenly makes them look not quite qualified to be president. And then the surge becomes a quick slide downward.

Still, the Sanders surge isn’t necessarily a fad. Many Democratic voters “feel the Bern” and they resent jibes by Washington insiders who denigrate Sanders as a temporary phenomenon.

Bernie Sanders has weaknesses, of course — all candidates do. But what might enable him to keep going through the fall, through Iowa and New Hampshire, to the Democratic convention?

There are a lot of intriguing questions about the Sanders candidacy — and until those questions are answered by voters, it doesn’t seem fair to write him off as an eccentric who doesn’t have a chance at winning the nomination.

Contrast With Hillary — Conviction Vs. Expediency

A big part of Sanders’ appeal is that he is a true believer, and he’s been generally consistent in his views — even when that has meant going against majority opinion. Even people who disagree with him on basic issues can respect him for being true to his principles. That is not something you hear people say about Hillary Clinton. Indeed, journalist Carl Bernstein (famous for investigating the Watergate scandal for the Washington Post) recently said Clinton is a “specialist in fudging facts."

Sanders is consistent in his philosophy, but he has also shown a willingness to compromise to get results. For example, Jill Lawrence recently wrote in Politico magazine, “How Bernie Sanders Fought for Our Veterans -- One of America’s biggest ideologues knows how to make a deal.” By contrast, Clinton supporters have had trouble answering the question: What has she accomplished as senator or secretary of state? Worsening conflicts in the Middle East don’t help on that score.

A Debate Between Bernie, Hillary And Hillary

If you listen to a Sanders interview, you might notice that his answers are optimal for a debate — they are not usually one to two sentence sound-bites, but rather one-minute answers. By contrast, Clinton tends to offer very brief answers-- usually general or vague, and often evasive. That might work if the goal is mainly to avoid making mistakes, but it doesn’t work well in a debate where voters expect to hear something genuine, interesting and hopefully inspiring.

A huge problem for Clinton in those debates will be explaining why many of her positions on key issues are radically different from those she espoused not many years before. For example, she’s flip-flopped on marriage equality, criminal incarceration, trade, etc. She’s lurched leftward in recent months to try to keep Sanders from outflanking her with progressives, but in a debate she’ll be pressed to explain why those changes weren’t just politically motivated. Sanders can quote her, and cite past positions (like her vote to authorize military action against Iraq), and she won’t be able to dodge the obvious. She’ll have to admit that her views have changed on issue after issue, and Sanders can make the case that he has not only been ahead of the curve on liberal causes, but actually helped bend the curve. How can Clinton come out ahead in such a debate?

Money + Message + Media = Momentum

Clinton has raised substantially more money than Sanders, not surprisingly — but it’s the large donations you expect to see for an establishment candidate, whereas Sanders has small donations (average $33) from a great many more people. Indeed, he has many more donors at this stage -- 250,000 individual donors — than Barack Obama when he faced Hillary Clinton in 2008.

Money can only do so much in presidential campaigns. Many candidates have raised and spent millions yet won very few delegates. Money is needed, of course, but the advertising it can buy is usually less effective than the publicity and buzz generated by the candidate and the message. That’s what we’ve been seeing with Sanders. He has drawn bigger crowds than any other candidate in this election cycle, but more than that, those in attendance seem impressed by his performance. Clinton has not turned on her audiences in that way. In fact, her handlers have tried to limit her exposure to voters who might ask unhelpful questions. If a campaign doesn’t have confidence in the candidate’s ability to perform under pressure, that usually doesn’t end well.

Sen. Bernie Sanders, I-Vt., speaks about his agenda in running for president, Thursday, April 30, 2015, on Capitol Hill. (Jacquelyn Martin/AP)

Will Elizabeth Warren Endorse Sanders?

Recently Sen. Warren effusively praised Sanders: “Bernie’s out talking about the issues that the American people want to hear about. These are people who care about these issues, and that’s who Bernie’s reaching. I love what Bernie is talking about. I think all the presidential candidates should be out talking about the big issues.”

By comparison, a few months ago Warren was only lukewarm in talking about Hillary Clinton. When asked by Al Sharpton, “A lot of progressives have questions about whether she’ll (Hillary Clinton) be a progressive warrior; what would you say to them?” Warren replied: “You know, I think that’s what we gotta see. I want to hear what she wants to run on and what she says she wants to do. That’s what campaigns are supposed to be about.”

If Warren continues to sound pro-Sanders while expressing skepticism about Clinton, many progressives who had hoped for a Warren presidential candidacy will interpret that as a quasi-endorsement of him. At least it would signal that progressives should feel free to vote their conscience, rather than their calculations about who’d be more electable in a general election. It would also undercut Clinton’s main argument for why liberals should be inspired to vote for her: to make history by electing the first woman president. If that isn’t a sufficient reason for Warren, other progressives might feel the same way.

Who Will Inspire Democratic Voters?

President Obama has enjoyed a surge of his own — his popularity has risen in recent months. Do Democrats want to be inspired by their next presidential nominee or do they accept the argument that electability is the issue? The problem for Clinton is that many Democrats in Iowa and New Hampshire might decide that it’s safe to vote for the underdog Sanders as a protest against “Wall Street and the billionaire class,” as Sanders puts it. And if many of those voters vote that way, and Clinton loses both states … well, her electability and inevitability arguments would collapse. How could she plausibly argue that she would be the stronger candidate if she lost both states? That might not seem likely to happen, but it is possible. And the Sanders campaign is fueled by the idea that anything is possible — or as another underdog once put it, “Yes, we can.”

Todd Domke is a Republican political analyst for WBUR.