Sen. Bernie Sanders (I-Vt.), a White House contender in 2016, is known for his stances on budget issues and war. Here's the Vermont senator's take on Obamacare, Social Security and more, in his own words. (Julie Percha/The Washington Post)

Do you feel the Bernie-mentum?

Yes, of course, I am talking about the presidential candidacy of Sen. Bernie Sanders, which the independent/socialist from Vermont made official last week on the shores of Lake Champlain.

And, no, I am not being entirely flip. The truth of the matter is that Sanders has quickly emerged as the leading rival — and liberal alternative — to the juggernaut candidacy of former secretary of state Hillary Rodham Clinton.

On Saturday in Iowa City, more than 400 people crowded into a recreational center — some sitting on exercise balls — to hear the senator speak. That included a pair who drove from Oklahoma City — 8 1/2 hours away! — to hear him, according to reporting by the Iowa City Press-Citizen.

And it’s not just anecdotal evidence that suggests Sanders’s movement in the race. Witness new polling from Quinnipiac University on the Democratic field: Clinton leads the way with 57 percent, followed by Sanders at 15 percent, Vice President Biden at 9 percent, and Martin O’Malley, Jim Webb and Lincoln Chafee all at 1 percent. Sanders’s growth from the last poll is even more eye-catching; he was at 8 percent in an April Q poll, and 4 percent in a March one.

Fifteen percent, of course, is still 42 points behind Clinton. Which means that Sanders is unlikely to seriously challenge the front-runner for the nomination at this point. What Sanders has proved over the past month or so, however, is that O’Malley, Webb and Chafee will have to go through him if they want to be the alternative — liberal or otherwise — to Clinton in the race. (In the Q poll, 28 percent of very liberal Democrats name Sanders as their preferred candidate.) That status is a genuine accomplishment for Sanders and his campaign team.

Below are the latest rankings of the five people with the best chance of winning the Democratic nomination next year. The No. 1 candidate — HINT: It’s Clinton — is the favorite.

5. Biden: If the vice president wanted to challenge Clinton, he already would have done it. Given the personal tragedy of losing his eldest son over the weekend, it’s hard to imagine that Biden is terribly focused on his next political steps at the moment.

4. Webb/Chafee: Webb, the former senator from Virginia, and Chafee, the former senator and Rhode Island governor, are not alike in almost any way — including ideologically. (Chafee is more liberal than Webb.) But they share a spot in our rankings because both are likely to run for president and barely register in any polling.

3. O’Malley: The former Maryland governor announced his presidential bid Saturday, to generally positive press. He has the right profile to be a liberal alternative to Clinton — he spent his second term as governor building his résumé on issues such as gay marriage and the death penalty — but Sanders has aced him out, at least at the moment, for that spot. Still, O’Malley probably will have an infrastructure in early states that Sanders will struggle to match, so he could well make up that lost ground. Also, he plays the guitar.

2. Sanders: It has been a terrific past month for Sanders. Does he have a second act? Does he need one? The problem for Sanders — or anyone running to the ideological left of Clinton — is that there just isn’t all that much space there. She took 61 percent of self-described “very liberal” voters in that national Q poll — four points better than she did with the broader Democratic electorate.

1. Clinton: The focus continues to be on the Clinton Foundation, her private e-mail server and her lack of press access. But Clinton and her team seem comfortable largely ignoring all of that as they continue to execute her low-profile (or as low-profile as she can be) visits to early states. Even for all of the bad headlines, Clinton remains the biggest non-incumbent front-runner in modern presidential history.

Former U.S. senator and secretary of state Hillary Clinton announced that she’s running for president in 2016. Here's the Democrat’s take on women’s rights, Benghazi and more, in her own words. (Julie Percha/The Washington Post)