 -- Bernie Sanders swept through Massachusetts Saturday, drawing large crowds in both Springfield and Boston.

More than 20,000 people came out to see him in Boston, filling the stadium floor at the Boston Exhibition and Convention Center. A few thousand did not fit inside but stayed in cold weather and watched the speech on screens in an overflow area outside.

"You guys are the true believers," Sanders said, addressing those in the dark outside who gave him a celebrity's welcome after his hour and half speech inside the arena.

"Thank you for freezing out here," he continued standing on a platform with a microphone and waving to the crowd over their cheers. "Were you able to see the speech?

"What we have got to do -– and your presence out here tonight is half way here -– what we have got to do is to make a political revolution where we involve people in the political process in a way they have not been involved before," he told them.

It was Sanders' first day back on the campaign trail since announcing impressive fundraising numbers for the quarter this week, on pace with Hillary Clinton. And while Sanders has called for a grassroots movement and a "political revolution" since the first day of his campaign, he emphasized these ideas even more today.

"Our campaign is a different type of campaign. It is a grassroots campaign, designed not only to elect someone to be president of the United States, but to build a political movement," he said in Springfield.

Later in Boston, he continued on the same theme.

"I am enormously proud," he said. "As some of you may have noticed, we have raised tremendous sums of money, because 650,000 Americans made contributions average $30 apiece.

"In other words words we are running a people's campaign," he said. "And the millionaires and billionaires may have more money than we do, but we have something they don't have. Look around this room -- this is what we have."

The line to get into the Boston event was at one point five blocks long. A team of nearly 300 volunteers ran up and down it, signing people up on the campaign mailing list as they waited. More volunteers were stationed at entry tables with computers logging contact information, handing out donation forms, and selling merchandise –- more than $13,000 worth in total, according to the campaign. Many in the crowd brought homemade signs.

The Springfield rally drew approximately 6,000 fans.

"The energy has just gotten so strong," said Raymond Bazydlo from Essex, New York, who said he has been to several of Sanders' campaign events along the East Coast. "I see the crowds seem to be getting younger and the enthusiasm is getting greater."

Dorthody Albrecht, a teacher from Holyoke, Massachusetts, said because she is from Massachusetts, which neighbors Sanders' home state of Vermont, she has been aware of Sanders' record for some time.

"I support Bernie Sanders, because I feel he is not bought," she said.

Asked why she thought he was having so much success she said, "I think that is about taking back our system of government from the people who bought it, and the only way to do that is through utilizing our one vote, and we’re going to have to all support him."

Sanders did not mention any of his opponents by name, but did give a shout-out to Massachusetts senator and torchbearer of the progressive movement, Elizabeth Warren.

He also made specific mention of the school shooting in Oregon this week, saying that people were "sickened" and "bewildered" with the ongoing gun violence in the country. Sanders has a a mixed voting record on the issue. He voted against the Brady Bill which back in 1993, which mandated background checks, in part because it called for longer waiting periods before gun purchases. Sanders is instead in favor of instant background checks.

"Guns should not be in the hands of people who should not have them," he said in Boston Saturday. "We have an instant background system right now that needs to be strengthened."

He spoke against the so-called gun show loophole, and in favor of more work for mental health.

"We need a revolution in terms of mental health in this country," he said, adding that people regularly call his Senate office seeking affordable help for loved ones.