Both women took the stage at the Haas Theater at People's Light and Theater in a moderated conversation with Cheney, the daughter of former Vice President Dick Cheney.
"We have the chance to elect somebody who you know is going to defend the rule of law. You know Vice President Harris is going to defend our constitution," said Liz Cheney.
Speaking about her choice to endorse Harris, Cheney said that "every single thing in my experience and in my background has played a part."
Harris, who has struggled to detail differences between herself and President Biden, offered up a line she has used in recent days when asked specifically about the differences: "Mine will not be a continuation of the Biden administration. I bring to it my own ideas, my own experiences."
Since 2016, Chester County has seen an increase of about 25,000 registered Democrats and virtually no change in registered Republicans.
Democratic volunteer Tina Floyd has been canvassing for Harris.
"I'm surprised at the number of independents voting for Kamala Harris and occasionally some Republicans," she said.
"I'm not necessarily a big endorser of Harris but I'm a huge opponent of what I see in Trump," added Don Lessem of Aston.
A Feasterville McDonald's closed for the day on Sunday so former President Donald Trump could take questions while filling orders from supporters.
On Monday, he delivered remarks to residents affected by Hurricane Helene in Asheville, North Carolina.
"When I'm president, I will stand with you until communities are fully rebuilt," he said, criticizing the administration's handling of the crisis.
"In the wake of this horrible storm, many Americans in this region felt helpless abandoned and left behind by their government," Trump added.
Harris is expected back in Pennsylvania on Wednesday, and Trump is expected back this week but a date has not been announced yet.
READ MORE: Trump works fry station, holds drive-thru news conference at Bucks County McDonald's
Trump works fry station, holds drive-thru news conference at Bucks County McDonald's