MILWAUKEE >> With three weeks left in the presidential campaign, Democrat Kamala Harris is spending most of her days trying to shore up support in the “blue wall” states of Pennsylvania, Michigan and Wisconsin as she tries to avoid a repeat of Hillary Clinton’s collapse there eight years ago.

The vice president campaigned at a hockey rink on Monday in Erie, Pennsylvania, where she denounced Republican candidate Donald Trump as “unhinged.” She visited an art gallery in Detroit with actors Don Cheadle, Delroy Lindo and Cornelius Smith. Jr. on Tuesday, then recorded a radio town hall with Charlamagne tha God.

On Wednesday, Harris was back in Pennsylvania to stress allegiance to the Constitution as she stood just steps from the banks of the Delaware River, where George Washington crossed with his troops in a pivotal moment of the Revolutionary War.

Her pace doesn’t let up for the rest of the week. Harris was holding three events Thursday in Wisconsin, where she started with a meet-and-greet for students at the University of Wisconsin-Milwaukee before heading to two rallies. She has three events in Michigan on Friday and will be in Detroit on Saturday.

A loss anywhere in the “blue wall,” a name that reflects the region’s traditional Democratic leaning, could doom Harris’ path to the presidency.

“You don’t take those states for granted. And she’s not,” said Joel Benenson, a Democratic pollster.

He previously served as chief strategist for Clinton, whose campaign was so overconfident that it stopped conducting its own polls in Midwest battlegrounds as the election approached.

“We’ve got a painful lesson in 2016 when we didn’t go to the ‘blue wall’ states, and we lost,” Benenson said.

Harris’ campaign emphasized that she’s not giving up on Sun Belt battlegrounds like North Carolina, Georgia, Arizona and Nevada. The vice president was in North Carolina over the weekend and she’s expected to be back in Georgia on Sunday.

But any candidate’s most precious resource is time, and Harris’ schedule reflects the consensus about her most likely shot at winning the White House.

“It’s not the only path, but it’s the easiest path to victory,” said Democratic pollster Celinda Lake.

She added, “If you can’t win Pennsylvania or Michigan, do you really think you can win Georgia or North Carolina?”

Pennsylvania and Michigan are Harris’ most popular destinations since Labor Day, with eight stops in each state, according to an Associated Press tracking of candidates’ public events.

At Harris’ event in Washington Crossing on Wednesday, one voter said Democrats had discovered the cost of complacency the hard way.

“In 2016, we thought we had it, you know, we thought we were okay,” said Melanie Woods, a retired school principal who came all the way from Brooklyn. “And I don’t think you can ever take anything for granted any more.”

Dan Kanninen, the Harris campaign’s battleground states director, said the vice president has “multiple pathways” to win.

“All seven battleground states are in play, and we know each will be incredibly close,” he said. “That is why we will continue to engage and mobilize voters aggressively across all these states until Election Day.”

During her campaign travels, Harris is trying to pick strategic areas to talk about key policies, such as promoting auto jobs and union membership in Detroit and going to Douglas, Arizona to unveil plans to tighten rules for immigrants seeking asylum at the U.S.-Mexico border after she walked along the towering wall separating the two countries.

The campaign is also increasingly relying on large organizational networks in key states, including coordinated offices with state Democratic parties, to fill in the gaps when Harris isn’t there. It’s deploying key surrogates — most notably Harris’ running mate, Minnesota Gov. Tim Walz — to lessen the impact of choosing to travel to one part of the country versus the other.