Vice President Harris is ratcheting up warnings about what President Trump will do in a second term, a Halloween strategy of placing the most frightening specter of him before the American people. It’s a gamble with risks. If the former president prevails on Tuesday, expect him to claim a mandate to do much of what his opponents have been saying he will do. 

The concept of a presidential mandate has faded across three decades of narrow victories. President George H. W. Bush earned 53.4 percent of the popular vote in 1988 — a clear message to carry forward President Reagan’s policies, which had earned the Gipper two landslides. In the eight elections since, no president has matched that high-water mark and four have fallen below 50 percent. 

Candidates have interpreted this trend to mean that Americans are leery of big ideas and quick turns right or left. Instead, campaigns promise “common sense solutions” — a soothing and opaque phrase that invites voters to infer their own priorities. It frees presidents from promising too much and delivering too little. 

Trump rejects this safe course. In“The Art of the Deal,” he described the tactic as “bravado” and “truthful hyperbole” offering insight into his lack of shyness. “People may not always think big themselves,” he wrote, “but they can still get very excited by those who do.” 

In the May 30 episode of “Conversations with Bill Kristol,” the Democratic strategist, James Carville, observed that Trump was “really laying the groundwork to say, ‘I ran on this. I told you I was going to do this. Now I’m going to do it. … I’m not doing it like you tell me to do it. I’m doing it my own way’ — and by the way, he’ll have a point if he wins.” 

Trump, Mr. Carville said, “told you on day one what he was going to do. He told you the kind of people that he was going to appoint and he’s going to take that as a complete justification to do whatever” he wants to do. “I didn’t hide it from the voters,” Mr. Carville envisioned Trump saying. “I told them.” 

Democrats have muddled this scenario by making the election a referendum on Trump personally. They’ve made charges that he’ll set up internment camps for political foes, “weaponize” the Justice Department, pull out of the North Atlantic Treaty Organization, and ban abortion. That the 45th president has repudiated any such plans hasn’t stopped them from becoming issues before the people. 

Trump has also dismissed the allegations of Ms. Harris and President Biden that he’ll be a “dictator” and end democracy. In her speech on Tuesday, Ms. Harris said that Trump plans to “cut Medicare and Social Security” and intends to repeal the Affordable Care Act, known as “Obamacare.” 

Again, Trump has rejected these charges. He does propose the “largest deportation operation in American history” to send those with no legal right to be in the country back home. When Ms. Harris twice mentioned that Trump plans “a trillion dollars in tax cuts for billionaires and big corporations,” she was also close to the mark. 

Trump’s aim to rid the federal government of employees insulated from the will of the people as expressed in elections, which he calls “the deep state,” is also a top agenda item. A Trump victory will raise the question of just how much of Ms. Harris’s Trump Halloween mask voters wanted versus the Republican’s actual proposals — and it would be up to him alone to decide. 

Winning the popular vote might strengthen Trump’s hand, but anyone who achieves 270 electoral votes is president, just as the person who graduates last in medical school is called “doctor.”

That’s illustrated by a story told by aide to President Kennedy, Richard Scammon, who said he once asked about “the mandate” of the senator’s 49.7 percent victory in 1960. “Mandate, schmandate,” Scammon quoted Kennedy as saying. “I’m sitting here.” He meant, he was sitting there as president-elect.

Returning a defeated president to the Oval Office, as it was the one time it happened in American history, would be an implicit rejection of the administration that replaced him four years prior. If voters decide to give Trump that distinction. expect him to claim a mandate.