“This is one man trying to do to our American self-government what no king and no foreign power has ever managed to do,” Gov. Gavin Newsom of California, a Democrat considering a run for the White House, said of Mr. Trump. The governor’s speech focused heavily on the president’s 2020 election falsehoods and efforts to reshape election rules before the midterms.

Gov. Wes Moore of Maryland, another potential 2028 Democratic contender, said that “the very premise of patriotism is under attack.” He did not mention Mr. Trump by name in the speech but repeatedly alluded to him.

For ambitious politicians in both parties, the holiday weekend offered an opportunity to outline mission statements for their brands of politics, while tying them to traditional notions of patriotism.

America’s 250th birthday came at a particularly polarized moment. Politicians have long used July 4 as a backdrop to make political appeals and engage with voters, but historians said Mr. Trump’s aggressively partisan and personalized approach to the holiday was unique.

Some Democratic-led states refused to participate in the Trump-backed Great American State Fair on the National Mall in Washington, another illustration of the stark divides in the country.

Former President Bill Clinton issued a statement saying that he was concerned about the “deep division” in the country. He argued that the Trump administration had brought the country “close to the edge” with its immigration crackdown and what he described as an “unconstitutional war” with Iran. He said he found hope in people lining up to vote.

Mr. Newsom argued in his speech, filmed in the Governor’s Mansion in Sacramento and released Saturday afternoon, that Mr. Trump embodied the “very behaviors our founding fathers fought against.”

The governor said he was working with state lawmakers to create new safeguards blocking the seizure of ballots, accusing the president of “measuring how far he can go” to undermine elections and “shred” the Constitution.

In Georgia, the focus of many of Mr. Trump’s efforts to reverse the 2020 election, the F.B.I. is assigning investigative analysts to check records, and in California a Republican sheriff this year seized hundreds of thousands of ballots from a 2025 election. Mr. Trump has also made baseless claims about election fraud in the race to replace the term-limited Mr. Newsom.

Mr. Moore, speaking to a roomful of military veterans at the Maryland State House in Annapolis, widened his focus beyond the electoral system.

The governor spoke of a “rewriting” of U.S. history under an administration that has banned books and purged records related to diversity and inclusion. He said the “politics of today feel like a grift.” And the governor, an Army veteran who has often criticized Mr. Trump over the Iran war, declared that “starting a war without a purpose is not patriotic” and that “ending a war without achievement is not victory.”

In an interview after the speech, Mr. Moore left little doubt that the president weighed heavily on him as he drafted his remarks. He said he wanted to offer a rebuttal to a strain of “small,” grievance-fueled nationalism that he said Mr. Trump exemplified.

“I wanted the country to remember how big this country is,” Mr. Moore said, urging Americans to embrace a form of patriotism centered on service rather than what he said was a nationalistic impulse to point “fingers at others.”

The White House did not immediately respond to requests for comment on Mr. Clinton’s statement or on the Democratic governors’ speeches. But as Mr. Moore was beginning his remarks, the president wrote on social media, “Has anyone ever seen a Happy Dumocrat?” Mr. Trump also mocked a pair of Democrats running in marquee Senate races.

A day earlier, Mr. Trump delivered a dark, partisan speech at Mount Rushmore, describing his political opponents as “godless” communists and saying that Republicans could only lose the midterm elections if they were “stupid and unwise.”

Communism, the president said, is the “enemy of July 4, 1776.” He has falsely suggested that democratic socialists who have won in a recent Democratic primary election are communists.

Mayor Zohran Mamdani of New York, a rising leader on the left who endorsed three victorious self-described democratic socialists in recent House primaries in New York, also delivered a speech tied to Independence Day.

In remarks from City Hall on Friday, Mr. Mamdani, surrounded by recently naturalized immigrants, critiqued what he described as a blind form of patriotism that he said fails to grapple with the country’s flawed history and takes a mistaken view of what makes the country exceptional.

“We are told that America is exceptional because we are richer, stronger, more powerful than everyone else,” said Mr. Mamdani, a Ugandan-born immigrant. “The truth, my friends, is that America is exceptional because here nothing is fixed into place.”

On Saturday, Vice President JD Vance pushed back in a speech that appeared to be in direct dialogue with Mr. Mamdani’s. He criticized those who, he said, speak “obsessively not of our national greatness but of our national imperfections.” And he dismissed what he said was “zero-sum” thinking that pits the powerful against the powerless and that only finds pride in the defeats of the well-off.

“Reject the two-dimensional view of your fellow citizens and reject the two-dimensional view of your country,” Mr. Vance, who is considered a potential 2028 presidential candidate, said aboard the U.S.S. Kearsarge in New York Harbor, within a few miles of where Mr. Mamdani spoke a day earlier. “Reject the view of your nation that sees only its sins, but not its grace and its greatness.”

Julian E. Zelizer, a Princeton history professor, said that politicians throughout American history have used Independence Day as an opportunity to articulate “what they stand for and what their parties stand for.”

Professor Zelizer said that “the politicians who are smart” would find a way to acknowledge the country’s divisions and show “what they’re going to try to do to try to close them.”

Laurel Rosenhall contributed reporting.