Vice President Kamala Harris on Wednesday made her most direct and expansive pitch yet to conservative and moderate voters, appearing in Pennsylvania with a phalanx of Republican elected officials who have set aside their party loyalties to try to defeat former President Donald J. Trump.

At a campaign event in Bucks County, Pa., Ms. Harris tried to strike a unifying tone even as she castigated her opponent, casting her campaign as one that embraced anyone who believed that Mr. Trump should not serve a second term.

“Our campaign is not a fight against something — it is a fight for something,” she said. “It’s a fight for the fundamental principles upon which we were founded. It is a fight for a new generation of leadership that is optimistic about what we can achieve together — Republicans, Democrats and independents who want to move past the politics of division and blame and get things done on behalf of the American people.”