Fifteen percent, of course, is still 42 points behind Clinton. Which means that Sanders remains a non-threat to seriously challenge the frontrunner for the nomination at this point. What Sanders has proven over the last month or so, however, is that O'Malley, Webb and Chafee will all have to go through him if they want to be the alternative -- liberal or otherwise -- to Clinton in the race. 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 ranked candidate -- HINT: It's Clinton -- is the favorite.
5. Vice President Biden: If Biden wanted to challenge Hillary, he'd already have done it. It's simply too late for the vice president to get in now as the vast majority of establishment support he would try to line up is already unified behind Clinton. And he didn't have much of a chance anyway. (Previous ranking: 3)
4. Jim Webb/Lincoln Chafee: Webb, the former Virginia senator, and Chafee, the former Rhode Island senator and 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 they are both likely to run for president and both likely to barely register in any polling while doing so. (Previous ranking: 4)
3. Martin O'Malley: The former Maryland governor is, as expected, going to run -- with an announcement set for Saturday in Baltimore. He has the right profile to be a liberal alternative to Clinton -- he spent his second term as governor building that resume -- but Sanders has aced him out, at least at the moment, for that spot. Still, O'Malley will likely have an infrastructure in early states that Sanders will struggle to match, so could well make up that lost ground. Also, he plays the guitar. (Previous ranking: 2)
2. Bernie Sanders: It's been a terrific last month for Sanders. Does he have a second act? Does he need one? (Previous ranking: 4)
1. Hillary 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 so much noise and 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 frontrunner in modern presidential history. (Previous ranking: 1)