In 2007, candidate Barack Obama, drawing rockstar crowds on his way to the White House, held a rally on Boston Common that drew 10,000 people. It was the biggest political gathering in Massachusetts in decades. On Saturday, Bernie Sanders brought more than twice that number, an estimated 24,000, to the Boston Convention and Exhibition Center — close to 20,000 inside the cavernous building and the rest watching a big screen outside.

One photo showing the scope of the event, posted by AlterNet writer Zaid Jilani, got the attention of a lot of political reporters:

Big as it was, the rally was just the third-largest of Sanders' campaign so far — after August events in Portland and Los Angeles. And by the way, Sanders spoke at event earlier Saturday in Springfield, Mass., that drew 6,000 people — which would by itself be a big event for any other candidate in the Democratic and Republican fields.

Sanders gave his standard stump speech, more than an hour, very heavy on issues: Wall Street greed, billionaires, Citizens United, the "real unemployment rate" of 10 percent, the Koch brothers, a $15 an hour minimum wage, the Walton family, American oligarchy, single-payer healthcare and much more. Sanders added some new material calling for gun control in the wake of the Oregon shootings, and also went out of his way to celebrate single motherhood in a fashion that would make social conservatives wince.

Sanders seemed particularly relaxed Saturday, allowing even a light moment or two in his relentlessly serious stump speech. Sanders told the crowd he had watched the recent Republican debate — "a very painful experience" — and was amazed at "the parallel universe that these folks live in." "In their world," Sanders continued, "every problem that you can possibly imagine is caused by Barack Obama. If it's raining, if it's too hot, if there's a mosquito in the room — it's all Barack Obama."

Why Boston? For Sanders, the rally was a two-fer. "The crowd included people from next door New Hampshire (where another poll today put Bernie ahead) and Massachusetts, a March 1 state," said Sanders spokesman Michael Briggs in an email exchange. "We are looking at Massachusetts as one of the 13 Super Tuesday states where we like our chances."

Many analysts believe Sanders faces trouble on Super Tuesday. African-American voters are a huge part of the Democratic coalition; at the moment, they support Hillary Clinton by large margins and will be voting in big numbers on Super Tuesday. Sanders, from Vermont, where blacks make up a tiny 1.2 percent of the population, has attracted mostly-white crowds and is showing strength in mostly-white early voting states like Iowa (3.4 percent black) and New Hampshire (1.5 percent black).

But Massachusetts, where African-Americans make up 8.3 percent of the population and Hispanics make up 10.8 percent, is a somewhat more diverse state. And Briggs pointed out that Sanders has already drawn "solid crowds" in some of those Super Tuesday states — Texas, Georgia and Virginia — where there will be a lot more black voters than in Iowa and New Hampshire.

"These appearances and others have shown that his message is resonating all over the country," said Briggs, "where big majorities, no matter what their politics, favor creating jobs, making college affordable, strengthening Social Security, addressing climate change, closing tax loopholes that let profitable corporations avoid paying any income taxes, and fixing the corrupt campaign funding system that the Supreme Court ushered in with Citizens United."

Of course, Hillary Clinton favors almost all of those things, too. But no one in ClintonWorld can be happy to see Sanders continuing to draw such big crowds in a race in which he wasn't even supposed to be a factor.