The benefits of incumbency already make beating Mayor Marty Walsh in November surpassingly difficult.

Now President Donald Trump has made it almost impossible.

Walsh has seen his national profile soar since Trump took office and threatened to withhold funding from cities like Boston if they refuse to help federal authorities round up undocumented immigrants who haven’t committed serious crimes.

Walsh has gone hard at the president over that, delivering a fiery speech in which he called Trump’s rhetoric “a direct attack on Boston’s people, Boston’s strength, and Boston’s values.’’ The mayor said he would even offer City Hall as a refuge for those vulnerable to raids: “If people want to live here, they’ll live here. They can use my office.’’

Days later, he was at Logan Airport with a bullhorn, denouncing Trump’s order blocking refugees, and travelers from seven majority Muslim nations, from the United States.

“I’’m here because this is not who we are as Americans,’’ he told reporters.

People are paying attention. Millions have watched video of Walsh’s speech offering City Hall as shelter. Last week, Trevor Noah interviewed the mayor on “The Daily Show,’’ and the great Samantha Bee featured him prominently in a spot on “Full Frontal.’’

“In the ongoing battle over whether to deport 11 million people, an unlikely hero has emerged,’’ she said. “America’s mayors: resolute, compassionate, and quivering with joy that they get to be on TV for something other than a hurricane.’’

Watching Walsh’s national star rise over the last few weeks makes you feel bad for City Councilor Tito Jackson, the only person brave enough to mount a credible challenge to the mayor this year.

It’s hard enough to compete with an incumbent who headlines events where you’re looking for votes, who dispenses treats to constituents while you can only promise them, and who raises campaign millions as you’re struggling to break 100 grand.

Now, Walsh isn’t really running against Jackson at all, but against a president who threatens everything this majority-minority city has come to stand for.

In an ordinary year, Walsh and Jackson would be arguing over whether the mayor has done enough to improve schools, whether he has listened closely enough to the concerns of people of color, whether his administration reflects a new Boston or is more of a throwback.

But right now, it’s looking like this election will not turn on whether Walsh has shoveled the streets fast enough or whether he has a grand enough vision for the city. Trump is president, and the mayor has promised to protect us. Not just promised, but really stuck out his neck, almost daring Trump to hit back.

Given to bouts of naked revenge, Trump could hit back, depending on whom he chooses to replace US Attorney Carmen Ortiz, whose office has been investigating union ties to Walsh’s City Hall. An awful appointee could bring a politically motivated hammer down on Walsh. Of course, an ethical appointee could do so, too, and Walsh would be still able to call it payback.

Walsh comes by his stand against the president’s odious edicts honestly. His own parents immigrated from Ireland. As with Latino and Muslim immigrants today, discrimination was commonplace.

“The majority of immigrants in this country aren’t committing a crime, they’re working one and two jobs trying to earn a living and raise a family and send money back home,’’ Walsh said in an interview. He sees fear among kids in the schools he visits.

“I can’t have families in the city of Boston who are fearful,’’ he said. “My role as mayor is to help everyone, and I can’t jeopardize that for potentials, for the loss of funding, and whatever else comes down.’’

He means it. But sometimes, a heartfelt position can be a politically useful one, too.

Globe columnist Yvonne Abraham can be reached at yvonne.abraham@globe.com. Follow her on Twitter @GlobeAbraham.