Now leading in presidential polls among Democrats in Iowa and New Hampshire, Vermont Senator Bernie Sanders drew huge crowds in Massachusetts on Saturday as he sought to attract donors and build a political infrastructure that will boost his campaign a month after the first two states vote.

Sanders addressed a near-capacity crowd of 20,000 at the Boston Convention and Exhibition Center, with a few thousand more watching a feed of his address while on Lawn on D. Hoping to secure a good spot at the event, people formed a line that stretched a half-mile down Summer Street, nearly reaching South Station two hours before the event began.


It was the third-largest rally Sanders has held this year, smaller only than events in Portland, Ore., and Los Angeles in August. To put it in context, the number of people who showed up to see Sanders at the convention center was nearly three times the population of Montpelier, the capital of the US senator’s home state of Vermont.

It is also the largest rally for a presidential primary candidate in recent Massachusetts history, topping 10,000 people drawn to Boston Common eight years ago by Barack Obama. In 1968, the Globe reported that Democratic presidential candidate Eugene McCarthy addressed 45,000 in Fenway Park.

Earlier Saturday, Sanders addressed a rally in Springfield, where 6,000 showed up to hear him, according the operations manager at the MassMutual Center.

On the way from Vermont to Massachusetts, he also spoke to about 120 people involved with New Hampshire State Employees Association in Manchester.

For 75 minutes Saturday evening, Sanders addressed progressive domestic causes ranging from same-sex marriage to income inequality to health care and the Black Lives Matter movement.

“In America today, we are living in a country that has more income inequality than any other country on earth, and it is worse today that it has been at any point since 1928,” Sanders said.

The self-described socialist said it was not a “left-wing idea” to call for the federal minimum wage to be raised to $15 an hour from $7.25.


“Wages in America are just too damn low,” he said.

These ideas, he told the overflow crowd after his main address, are achievable and not some “liberal utopia.”

Sanders also touched on issues that have dominated headlines in recent days, such as the mass shooting at an Oregon community college, the deteriorating situation in Syria, and foreign policy in general.

“We know the world in which we are living in is getting crazier and crazier by the day,” Sanders said.

“What I believe is that the United States of America has got to use all of its clout in every way so we can create a world in which we remove war as a means to solve problems.”

While most Democratic and Republican candidates are focusing their campaigns on Iowa, New Hampshire, South Carolina, and Nevada, which kick off the presidential nomination season early next year, some campaigns are looking ahead to the 11 states, including Massachusetts, that will hold Democratic contests on March 1.

Indeed, Sanders’s visit to Massachusetts came just after Hillary Clinton’s trip to the state on Thursday, when she held a policy event in Boston on drug abuse and addiction, in addition to big-money fund-raisers in Holyoke, Boston, and Belmont.

In 2008, Clinton secured a strong victory in the Massachusetts primary, even though then-US senator John Kerry and then-governor Deval Patrick had endorsed Obama in that contest.

“Clinton is certainly the heavy favorite for the nomination as a whole, but Massachusetts is the kind of state where Sanders could run strongly,” said Boston College political science professor Dave Hopkins. “His base of support within the party is centered among well-educated white ideological liberals, who constitute a significant share of the Democratic primary electorate in Massachusetts.”


Hester Murray, 59, of Belmont, said she wanted to see Sanders because she feels “unenthusiastic” about Clinton.

“There is something limiting around her as she expects to be the nominee,” said Murray, who is uncommitted in the presidential race and said she would attend a Clinton rally to hear her out.

Demographically, the crowd in Boston skewed toward the younger side, such as 25-year-old Haley Houseman of Medford.

Houseman said her friends got her interested in Sanders, so she decided to check him out.

“I heard a lot of great things about him, and how often do you get to see a presidential candidate 30 minutes from your home?” Houseman said.

But Jose Santos, a 52-year-old IT specialist from Everett, said he simply trusts Sanders more than Clinton regarding the issues he cares about the most: climate change, banking regulation, and immigration reform.

James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell, or subscribe to his daily e-mail update on the 2016 campaign at bostonglobe.com/groundgame.