MADISON, Wis. (AP) -- U.S. Sen. Bernie Sanders returned to the friendly terrain of Wisconsin on Friday, promising to build a coalition that will defeat President Donald Trump as he kicked off a swing through pivotal states that are part of the Democratic "blue wall" strategy for 2020.
Sanders, speaking to a crowd of about 2,400 who braved 40-degree (4 Celsiu) temperatures with a stiff 20 mph (32 kph) wind, pledged to flip Midwestern states such as Wisconsin that Trump narrowly won in 2016.
"Together, we are going to make sure that does not happen again," Sanders said to cheers. "We're going to win here in Wisconsin. We're going to win in Indiana. We're going to win in Ohio. We're going to win in Michigan. We're going to win in Pennsylvania and together we're going to win this election."
Sanders spoke in a city park along the shores of a lake, just a few blocks away from the state Capitol. Those in the crowd wore ski masks, winter coats, gloves and scarves as they cheered Sanders.
The independent senator from Vermont carried Wisconsin by 13 points in the Democratic primary three years ago and has been a frequent visitor since losing the nomination to Hillary Clinton. He touted his appeal to working-class and college-age voters, while fostering his network of supporters before this second run for president.
"He's the real deal," said Sanders backer Lynn Glueck, 50, a teacher from Madison who wore a winter coat with the hood up for the rally. She said to win, Sanders needs to emphasize his "long term integrity."
"It's not like he came up with these ideas the past two years, Glueck said. "He is not somebody who is bought and sold."
University of Wisconsin students Dylan Karls, 20, and Aaron Dwyer, 20, came from the nearby campus to check out the rally. They said they didn't know which Democrat they will vote for yet but liked that Sanders was forcing other candidates to take more liberal positions.
"I think he cares more than a lot of other politicians," Dwyer said. "He's a candidate people can get behind because he cares."
Democrats have made clear that their best chance at defeating Trump in 2020 is by winning back three states Trump narrowly captured: Wisconsin, Michigan and Pennsylvania. Dubbed the "blue wall" before they unexpectedly tipped to Trump, they may have supplanted Florida and Ohio as the nation's premier presidential battlegrounds.
Following the Wisconsin rally, Sanders was headed to Gary, Indiana, on Saturday. He'll hold a rally at a community college in Warren, Michigan, later that day, and then head to Pennsylvania for an event Sunday near the University of Pittsburgh and Carnegie Mellon campuses. Then it's off to Ohio on Monday.
Trump also knows the Midwest is vital to his re-election bid. He's looking to repeat in states he won in 2016 and expand his territory. Trump was due to campaign Monday in Minnesota, a state that almost went his way in 2016 after not voting for a Republican presidential candidate since Richard Nixon in 1972.
However, Democrats feel like the momentum is on their side in the Midwest. They captured governorships in Pennsylvania, Michigan, Wisconsin, Illinois and Minnesota last year.
The Sanders campaign said in a memo prepared in advance of the trip that the pathway to victory runs through the Midwest.
The memo said that Sanders has received donations from more than 8,000 people in Wisconsin, 14,000 in Michigan and more than 18,000 in Pennsylvania. Sanders was leading all Democratic candidates in fundraising as he tries to establish himself as the clear front-runner amid the crowded field.
Sanders' appeal in Wisconsin is clear. He won 71 of the state's 72 counties in 2016, defeating Clinton by 13 points. Sanders also narrowly beat Clinton in Michigan, but lost to her in Pennsylvania.
Early polling in Wisconsin, Michigan and Pennsylvania has shown Sanders ahead of other Democrats. Just this week, the Marquette University Law School poll showed Sanders leading a field of 12 Democratic candidates in Wisconsin.
But pollster Charles Franklin cautioned about reading too much into the numbers a full year before Wisconsin's April 2020 primary. Candidates with the best name recognition, like Sanders, typically fare better this far out compared with others mounting their first national runs for office, Franklin said.
The Sanders campaign said his message on trade, unions, working families and health care resonates in Wisconsin and throughout the Midwest. Earlier this week, Sanders unveiled his latest "Medicare for All" proposal, an idea that has influenced Democratic state lawmakers in Wisconsin who are advocating for similar statewide health insurance coverage.