With his receding hairline, his tufts of white hair and his metal-rimmed glasses, Bernie Sanders is nothing of a rock star, let alone a sex symbol. And yet, the independent senator from Vermont creates sensation these days in the U.S. and attracts great crowds as a presidential candidate.

"Whoa!" exclaimed the 73-year-old politician last Wednesday night, welcoming about 10,000 people gathered in a coliseum in Madison, the progressive bastion of Wisconsin. "Tonight, we have made a little bit of history," he added, boasting about having attracted the biggest crowd since the beginning of the campaign for the 2016 presidency, with all parties taken together.

And he did it again two days later in Council Bluffs, Iowa, where more than 2,500 people came to listen to his call for a "political revolution." No other competing presidential aspirant has managed to gather such a large crowd in this rural Midwestern state where the first caucuses of the race for the White House will take place in January 2016.

That's not bad for a self-proclaimed socialist who is determined to steal the Democratic nomination for the presidency from Hillary Clinton. In fact, should the former secretary of state start worrying?

Maybe, because the crowds are not the only factor that makes the American media talk about "Bernie mania" or "Bernie-mentum." There are also the polls. In New Hampshire, a state that will hold the first primaries in 2016, Bernie Sanders has reduced the gap separating him from Hillary Clinton from 31 to 8 points in less than two months, according to the WMUR/NBC measures.

In Iowa, the gap between the two candidates has decreased from 45 to 16 points within two months, according to the survey carried out by Quinnipiac University.

"Hillary Clinton should not be biting her fingernails over her situation in Iowa ..., but Bernie Sanders certainly can’t be ignored," says Peter Brown, assistant director of the Quinnipiac University poll. "Iowa Democratic caucus-goers are generally considered more liberal than primary voters in most other states, a demographic that helps his insurgency against Secretary Clinton, who is the choice of virtually the entire Democratic establishment."

In his speeches, Bernie Sanders does not attack Hillary Clinton up front yet, but he does not spare those who pull the strings in Washington and Wall Street.

"The message is resonating, not just in Wisconsin, but all over America: The people are sick and tired of establishment politics, establishment economics. They want real change," he said in Madison, promising at the same time to establish a single-payer health care system, to make public universities free and to force big banks to subdivide.

The speech of the senator from Vermont is largely in agreement with that of one of his colleague from Massachusetts, Elisabeth Warren, who sparked disappointment among liberals by giving up her aspiration for the presidency. Obviously, this speech is meaningful within the Democratic left, regardless of the messenger.

But it is still difficult to imagine a scenario that would allow Bernie Sanders to defeat Hillary Clinton, whose support is stronger — particularly among black people, a rather nonexistent electorate in Iowa and New Hampshire. The current success of the senator from Vermont is quite similar to the one of another politician from his state, former Gov. Howard Dean, who had illuminated the Democratic left in 2003 before imploding because of the Iowa caucuses.

The Revolutionary

Certainly, Bernie Sanders would be a tempting target for the Republicans. Born into a Jewish family in Brooklyn, he left his hometown at the end of the ‘60s to join students, hippies, labor organizers, environmentalists, anti-Vietnam War campaigners and other establishment opponents who wanted to start a revolution in Vermont.

Successively elected as a socialist mayor of Burlington, in the House of Representatives and the Senate, Bernie Sanders, even today, speaks about revolution. And the Republicans would not miss the opportunity to take out some of his writings on the subject, like The New York Times did in an article published on Saturday.

They might be particularly interested in an article published in an alternative newspaper under the title "The Revolution Is Life Versus Death." Bernie Sanders, then 30, describes the horror that office workers in a city like New York face, condemned to repeat the same "moron monotonous work" day after day. Here is an extract: "The years come and go. Suicide, nervous breakdown, cancer, sexual deadness, heart attack, alcoholism, senility at 50. Slow death, fast death. DEATH."

The least we can say, four decades later, is that the author of these lines is not moribund.