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President Obama at North High School in Des Moines on Monday.Credit Zach Gibson/The New York Times

DES MOINES — He may not be a candidate anymore, but President Obama could not help wading a bit into the high-octane campaign to succeed him on Monday, urging the state that holds the nation’s first caucuses to vote against candidates who rail against teachers or fail to support adequate federal financing for public education.

Returning to the state that propelled his first presidential campaign in 2008, Mr. Obama seemed a little nostalgic for the days when he wandered the towns and schools of Iowa seeking support — more innocent days when all still seemed possible, before the travails of nearly seven years in office, the days when, as he joked, he had no gray hair.

He flew here to meet up with a bus tour by his education secretary and hold a town-hall-style meeting on education policy. But he could not help noticing a hotel near the airport where, he said, he had stayed maybe 100 days in 2007 and 2008 and must still have frequent-customer points. He noted there were “a bunch of folks who want this job,” but added with a laugh, “I just can’t imagine what kind of person would want to put themselves through something like this.”

Speaking at North High School in Des Moines, Mr. Obama was asked to weigh in about the current candidates and started to beg off. “On this one, I’m going to wiggle around a little bit,” he said. “Right now, I’m going to try to stay out of the campaign season, partly because I can’t keep track of all the candidates.”

He made no mention of those running for the nomination of his own party, like former Secretary of State Hillary Rodham Clinton and Senator Bernie Sanders of Vermont, or one possible candidate, Vice President Joseph R. Biden Jr.

But, without mentioning names, he went on to criticize Republican candidates who go after teachers’ unions, as has Gov. Chris Christie of New Jersey, and he rebutted candidates who threaten to cut off funding to colleges perceived to be politically biased, as has Ben Carson, who is running second in polls here.

“If you hear a candidate say that the big problem with education is teachers, you should not vote for that person,” Mr. Obama said. “It is a hard job, and it is the most important job we’ve got, and folks who go into teaching don’t go into it for the money. They go into it because they’re passionate about kids.”

Mr. Christie has said teachers’ unions deserve a punch in the face, arguing that they have stood in the way of reform, more dedicated to their own interests than to students. “They’re not for education for our children,” he told Jake Tapper on CNN last month. “They’re for greater membership, greater benefits, greater pay for their members. And they are the single most destructive force in public education in America.”

Mr. Obama also responded to a questioner who asked about an unnamed candidate who proposed cutting federal funding to politically biased colleges. “I have no idea what that means,” the president said. “I suspect he doesn’t, either.”

In Iowa this summer, Mr. Carson said the federal government should monitor colleges. “The other function I would give to the Department of Education is monitoring our institutions of higher learning — colleges and universities — for extreme political bias,” he said. “If it exists, they get no federal funding.”

While Mr. Obama mocked that idea, he also said it would be wrong for colleges to avoid views that may be unpopular.

“I’ve heard of some college campuses where they don’t want to have a guest speaker who is too conservative or they don’t want to read a book if it has language that is offensive to African-Americans or somehow sends a demeaning signal toward women,” Mr. Obama said. “I’ve got to tell you, I don’t agree with that, either. I don’t agree that you, when you become students at colleges, have to be coddled and protected from different points of view.”

“Anybody who comes to speak to you and you disagree with, you should have an argument with them,” he added. “But you shouldn’t silence them by saying you can’t come because ‘I’m too sensitive to hear what you have to say.’ That’s not the way we learn, either.”

Mr. Obama came here to join an annual bus tour by his education secretary, Arne Duncan, and to promote a couple of new initiatives aimed at students who are getting ready to go to college. His administration is creating a scorecard with information about different colleges and universities — but not rating them, as once envisioned — and moving to make it easier to apply for financial aid.

These are issues that Mr. Obama has something of a personal interest in as his older daughter, Malia, applies to colleges. Asked what advice he gives her, he said he had urged her not to get too stressed about making it into a particular school. He also said he had nudged her to keep her grades up and to be open to new experiences.

But he acknowledged that his advice might carry less weight than it once did.

“Now this is assuming that Malia would listen to my advice,” he said to laughter, especially from the parents in the audience. “She’s very much like her mother at this point.”