IOWA CITY, Iowa — Two minutes into his stump speech in this strongly Democratic college town, Sen. Bernie Sanders, I-Vt., made his first of many references to President Donald Trump, calling him "the most dangerous president in modern American history."

A short time later, he told the crowd that Trump "embarrasses us every day," before attacking the president's health care promises. "I know it will shock you when I tell you he lied," Sanders added.

Then, at an appearance in New Hampshire on Sunday, he told the crowd how his governing style would differ from Trump's. "The underlying principles of our government will not be racism, sexism, homophobia and religious bigotry," he said. "The principles that our government will work on will be based on justice."

In his first swing through Iowa and New Hampshire, Sanders has been an anomaly among the Democrats vying for the White House, as he routinely uttered two words that other candidates have often avoided: "Donald Trump."

The president dominates Twitter feeds, news cycles and the political landscape in almost every corner of the country — except venues where Democrats with presidential aspirations are speaking to voters. Those Democrats are strategizing about how or whether to attack Trump explicitly, and in a twist, many are uttering his name rarely if at all.

Given Democrats' anger at Trump, it might seem natural for the party's hopefuls to frequently give voice to that fury. But most have concluded that they must show they can rise above ferocious attacks, especially if they hope to carry their message to a general election where not everyone shares their sentiments.

It's also an attempt to learn the lessons of the 2018 midterm elections, when victorious Democrats, especially in swing districts, generally focused on issues such as health care, education and job security, which polls show voters care deeply about.

Recent history suggests that getting into a verbal war with Trump often plays into his hands, as reflected in the fate of 2016 GOP rivals such as Sens. Marco Rubio of Florida, whom Trump dubbed "Little Marco," and Ted Cruz of Texas, who received the moniker "Lyin' Ted." Sanders got his own nickname: "Crazy Bernie."

Instead, many Democrats are taking the line that the election is about more than Trump. In a recent swing through Charleston, South Carolina, Sen. Cory Booker, D-N.J., made little mention of the president — except to urge voters to look beyond him.

"I know it's so motivating to turn on the TV every day and see somebody you so disagree with," Booker said. "We have got to understand this is not about him. It's about us. We should be motivated not by what we're against but what we are for as a country."

A few days later, Pete Buttigieg, the South Bend, Indiana, mayor who is weighing a presidential run, was asked by a reporter about Trump's absence from his remarks to voters in New Hampshire.

"At the end of the day, if all we're talking about is him, folks in communities like mine and around here will be saying, 'OK, well, no one's talking about us,' " he said.

Sen. Kamala Harris, D-Calif., has avoided using Trump's name even when she's clearly talking about him, instead decrying "powerful voices that are sowing hate and division among us" or declaring, "I will not conduct foreign policy by tweet."

That makes Sanders' approach stand out. His statement that "we must defeat Donald Trump" garnered sustained applause during a speech at the Iowa Fairgrounds on Saturday, suggesting that it's a line many Democrats — at least Sanders' crowd — want to hear.

And steering too clear of the president carries other risks. If some Republicans regretted getting into a war of words with Trump in 2016, others concluded that it had been a mistake to ignore him for much of the campaign, on the theory that he couldn't win.

Sanders' language reflects his message that he's best positioned to defeat Trump, as well as an effort to assume the mantle of a front-runner who is looking ahead to the general election.

"A central question for Democratic primary and caucusgoers is, who is the best candidate to take on and beat Donald Trump?" said Jeff Weaver, a senior Sanders adviser. "And I think Bernie Sanders provides a powerful contrast to Trump."

But Democratic pollster Celinda Lake said Sanders' attacks risk alienating older, female and black voters.

Sanders has "a 25 percent base that is fired up by this, that sent him $6 million in his first day," Lake said. "But is his job just to hang on to that base, or is his job to expand that base? I think others are going to find this too harsh — too much negative and not enough about the alternatives about what the Democrats provide."

Cheryl Ridgeway, a 61-year-old Iowa City resident who is undecided but leaning toward Sen. Elizabeth Warren, D-Mass., said she doesn't like candidates "fighting back and forth" with Trump, but she can see the need for someone who can engage him.

"I want someone who appeals to our better angels, our better nature, but sometimes you've got to fight back," Ridgeway said. "I'm trying to see if they can stand up to Trump instead of kowtowing. If someone can stand up to Trump and come out on top, I think that says a lot about how they're going to deal with policy, how they're going to govern."

Warren's path shows the risks of tangling with Trump, who has nearly 59 million Twitter followers. Seizing on disclosures that Warren years ago had claimed to be Native American on some documents, even though she is not a member of a tribe, the president began mocking her as "Pocahontas."

In an effort to fight back, Warren in October released DNA results that showed she had a Native American ancestor, though it was between six and 10 generations ago — a move that backfired. Many Cherokee leaders and other Native Americans were upset, feeling that Warren had appropriated their culture without being a part of it, and Warren later apologized.

Sanders, who has drawn significant crowds, can better weather the risk because he is not introducing himself to voters, his supporters say.

Other candidates' speeches include policy prescriptions wrapped in personal accounts of who they are and why they're running. For Sanders, who ran a strong primary campaign in 2016, that introduction may not be needed.

What he does need, many voters said in interviews, is to convince people that a 77-year-old white man who calls himself a democratic socialist can be the 21st-century face of a younger, diversifying Democratic Party.

Anti-Trump zingers set him apart from the other candidates, and they excited the crowds that endured cold, rainy weather to see Sanders in his recent Iowa swing.

"Donald Trump is the elephant in the room; there's no avoiding it," said Jeff Shotwell, 67, who knocked on doors for Sanders in 2016 and attended Saturday's rally. "All of this is going to boil down to who can go head to head with Donald Trump. Don't underestimate the power of the Jerry Springer mentality." Springer's television show featured shouted, angry confrontations.

Shortly after Sanders announced he was seeking the Democratic nomination, one supporter tried to turn the nickname bestowed by Trump, the 45th president, into a rallying cry.

"Listen, I don't care when 45 calls him 'Crazy Bernie,' because he is a just a little crazy," said Black Lives Matter activist and writer Shaun King, who helped introduce Sanders at his kickoff event in Brooklyn this month. "And I think all of us got a little crazy in us, if you know what I mean."

The Washington Post’s Annie Linskey, Sean Sullivan and Chelsea Janes contributed to this article.