President Donald Trump and his secretary of state, Mike Pompeo, want to intimidate Iran. In public statements, they’ve warned the Tehran government that if it doesn’t stop attacking drones and ships, American armed forces are ready to strike. But back home, Trump and Pompeo are destroying the solidarity that the United States would need in order to sustain a military confrontation. They’re turning Americans against Americans.

Trump’s behavior is a sharp break from the behavior of the most recent Republican president, George W. Bush. Like Trump, Bush lost the popular vote. To broaden his support, Bush spent his first months in office praising Democrats and reaching out to Americans who hadn’t voted for him. The charm offensive worked. In polls, most Americans agreed that Bush shared their values, cared about people like them, and was uniting the country. More than 60 percent said Bush was honest and trustworthy.

That paid off when Bush began to rally the country for a war in Iraq. Most Americans, including about 40 percent of Democrats, supported his call to arms. By the time Bush launched the war in March 2003, two-thirds of the country stood behind him. Only 1 percent of Americans said they opposed going to war because they didn’t trust Bush.

Trump has taken the opposite approach. Instead of broadening his base, he has savaged the 54 percent of voters who cast their ballots for other candidates. He has attacked these voters’ motives and celebrated their pain. At rallies, Trump revels in chants for the imprisonment of Hillary Clinton. At every opportunity, he smears former President Barack Obama. On Friday, in an NBC interview, Trump denounced Obama 18 times.

A president who talks that way about half of America makes it awfully hard for those Americans to rally behind him in a war of choice.

Last week, at a rally kicking off his reelection campaign, Trump said Democrats were “depraved.” “Our radical Democrat opponents are driven by hatred, prejudice, and rage. They want to destroy you, and they want to destroy our country as we know it,” said Trump. “Our political opponents look down with hatred on our values and with utter disdain for the people whose lives they want to run.” He concluded: “The Democrat Party has become more radical, more dangerous, and more unhinged than at any point in the modern history of our country.”

A president who talks that way about half of America makes it awfully hard for those Americans to rally behind him in a war of choice. And in Pompeo, Trump has found a secretary of state who shares his partisan animus. Pompeo treats every media appearance as an opportunity not to represent the United States but to represent the Trump administration in a relentless campaign against Obama and former Secretary of State John Kerry.

In January, Pompeo went to Egypt to outline Trump’s foreign policy in a major speech. He opened with an indictment not of Iran, Russia, or China, but of Obama. “Our leaders gravely misread our history and your historical moment,” Pompeo told the Egyptians. “We were timid,” he lamented. “Our desire for peace at any cost led us to strike a deal with Iran, our common enemy. … The age of self-inflicted American shame is over.”

In reality, Pompeo’s tenure is all about shame. He’s ashamed of Obama and Kerry, and he can’t stop talking about them. He blames them for the crimes of Iran (“All of these things Iran did happened because the previous administration appeased the Islamic Republic of Iran”), Russia (“I only wish the previous administration had been so serious about preventing election interference”), China (“The previous administration put us in a bad place”), and North Korea (“the previous administration … allowed Chairman Kim Jong-un to continue to advance his nuclear threat”). Pompeo has warned Kerry that he could be prosecuted under the Logan Act for speaking, as a private citizen, with Iranian officials.

Trump and Pompeo work hard to insult and antagonize America’s allies. Trump has picked gratuitous fights with France, Germany, and the United Kingdom, each of which is a party to the Iranian nuclear deal from which Trump unilaterally withdrew. On Friday, when NBC’s Chuck Todd pointed out that European countries didn’t think Iran had violated the deal, Trump replied, “I don’t care about the Europeans. The Europeans are going out and making a lot of money.” The president complained that European countries had “taken advantage of us for a long time.” Meanwhile, in an interview with Finland’s largest newspaper, Pompeo mocked the “many European nations” that signed the Paris climate accord. “I’m sure it was a good party. I’m sure it felt good to sign the agreement,” Pompeo jeered. On June 16, when Pompeo was asked about German skepticism of the Trump administration’s evidence of Iranian aggression, the secretary of state scoffed, “There are countries that just wish this would go away.”

These insults don’t play well in Europe. But the deeper damage is at home. In the latest Economist/YouGov poll, taken last week, 51 percent of Americans expressed an unfavorable view of Trump. Forty-four percent said their view was very unfavorable. Only 33 percent said the president was honest and trustworthy, while 50 percent said he wasn’t. Most respondents said Trump didn’t care much about people like them, and 41 percent said he didn’t care about them at all. In other polls, most Americans have said that they don’t think Trump shares their values or cares about average Americans. Only 11 percent say the country has become more united under his presidency. Sixty-two percent say it has become more divided.

This alienation has undercut Trump’s ability to rally America. In the YouGov poll, more people disapprove than approve of the way he’s handling Iran. Fewer than 50 percent say they would support “military action against Iran if it is proven that [Iran] is responsible for attacks on commercial shipping in the Persian Gulf.” When Americans are asked which government they believe in the dispute over Iran’s alleged aggression—the U.S. government or the Iranian government—only 46 percent say they believe the U.S. government. Fourteen percent believe Iran, and 40 percent say they’re unsure. People who voted for Clinton in 2016 are almost as likely to believe Iran (22 percent) as to believe the U.S. (27 percent). Perhaps that’s because 93 percent of Clinton voters say Trump isn’t honest or trustworthy.

A Politico/Morning Consult poll taken over the weekend shows a similar effect. In this poll, 54 percent of voters view Trump unfavorably. When these voters are told that Trump has threatened to use force in response to Iranian aggression, they say by a ratio of 3 to 1 that they “oppose further military action in Iran.” Thanks to their opposition, a plurality of Americans stands against the use of force.

Public opinion doesn’t settle whether war is a good idea. You can argue that Bush was wrong in Iraq or that Trump is right in Iran. But public opinion is crucial in determining whether a country can sustain a military campaign—and whether, as a result, its threats to use force are credible. That’s why Trump’s constant fighting at home has crippled his ability to fight abroad. Telling half your country to go to hell doesn’t just make you contemptible. It makes you weak.