MUSCATINE, Ia. — Sen. Cory Booker can preach like a minister, but he told hundreds of Iowans over the weekend that they shouldn't expect him or any other presidential candidate to single-handedly rescue the country.

"None of us are saviors," he said of the packed field of Democratic candidates.

In an interview, Booker said it worries him when politicians such as President Donald Trump hold themselves up as the sole answer to America's problems. At the 2016 Republican National Convention, Trump declared, "I alone can fix it."

Booker said voters should be wary of any such claims. "That was one of the things he's said that frustrated me the most — of all the horrible things he's said," the senator said, sitting in his campaign's RV as it rolled past eastern Iowa farm fields.

The New Jersey Democrat said he learned a tough lesson in humility after he moved to a poor neighborhood of Newark as a fresh, idealistic graduate of Yale Law School. He came in with an arrogant attitude that he could rescue the local residents. "People were like, 'We don't need you to save this neighborhood. In fact, you have a lot more to learn. You're the one that needs saving,'" he recalled.

The lesson was that people needed someone to help them work together to turn the troubled city around, he said.

Booker became a city councilman, then Newark mayor before being elected to the U.S. Senate in 2013. "I used to say to people, 'Hey, if you elect me your city councilperson, I'm going to warn you right now, I'm going to come and ask more from you than you've probably ever done before.' ... We've all got to get much more involved."

In his Iowa caucus campaign appearances, Booker often touts the city's turnaround, including the quality of its schools, number of jobs and return of businesses. But he always talks about how "we" improved Newark, not "I."

Voters' yearning for a savior bubbled up Saturday evening at a backyard meeting Booker held with voters in Muscatine.

The smoke from torches warded off bugs from the nearby Mississippi River as several dozen Iowans sat on a patio to hear the candidate. Booker spent 18 minutes giving a stump speech that built from easy-going humor into an emphatic sermon about his hopes for the country.

"We can be the nation that, as a prophet from the Scripture says, is a light unto all nations," he declared. "I believe that, and I know the one way to achieve that is not by dividing this country against itself, but by uniting this country in the cause of justice and shared prosperity."

When it came time for questions, voter Francie Williamson asked Booker to compare himself to President Barack Obama, a Democrat whom Williamson and many other Americans saw as a towering hero.

Williamson said she wishes Obama could still be president. "I love that man," she told Booker. "What I loved about him was I was inspired. I felt inspired. He was the first candidate who I was like, 'Yes! This is who I want to go for — instead of just against the other party.'"

Booker replied that he also misses having Obama and his wife, Michelle Obama, in the White House. "I really do love the way you're looking at this," he told Williamson. "Because we want a candidate — I want a candidate — who can inspire the best of who we are."

But he said voters will have a tough choice in selecting someone to carry on Obama's legacy. "You've got an incredible field of candidates. Some of the people are my best friends in politics," he said.

Booker added that voters should consider his record of tackling tough issues, including helping turn around Newark and in persuading Republicans in Congress to help pass a criminal-justice reform bill. And he said all Democrats should enthusiastically rally around whoever wins the nomination.

Williamson, 39, said in an interview afterward she was impressed with Booker but remained undecided about whom to support in the Iowa caucuses. She agreed with Booker's point that no candidate can be a savior. She realizes she and many other Americans tried to put that mantle on Obama.

"He couldn't lead us to the promised land. He wasn't Moses," she said. "I think Obama was definitely a lesson in how hard it was to make change in Washington."

Booker, who was making his fourth campaign trip to Iowa, is trying to break out from a pack of Democratic candidates trailing the leaders. His two dozen rivals include six fellow U.S. senators.

State Rep. Jennifer Konfrst, who has endorsed Booker, said many Iowans probably are aware of him as a media celebrity, but haven't seen him in person yet. He's an excellent speaker who shines in front of Iowa voters, she said after a house party for him in Newton Friday.

Konfrst, a Windsor Heights Democrat and Drake University journalism professor, was asked what the New Jersey senator should do to gain traction in Iowa. "More of that," she said, pointing to a house where he'd just held an energetic meeting with voters.

Konfrst said she's not worried that Booker's poll numbers have been fairly static in Iowa. His campaign has a solid organization here, which should be able to stay in touch with voters and steadily build support toward next February's contest, she said. "They're running a caucus campaign, not a popularity contest," she said.

Many voters in Booker's audiences are still shopping for a candidate. Dianne Stanley of Keokuk was one of them. She was a little skeptical of Booker when she went to see him speak at a Keokuk coffee shop Saturday morning. As she waited for him to arrive, she said she was leaning toward Sen. Elizabeth Warren of Massachusetts.

Then Stanley listened to Booker's upbeat words about restoring hope and justice. She heard his emotional pleas to make the election about more than defeating Donald Trump. When the event was over, she came out of the coffee shop with her eyes glistening. "When someone talks that way about the dreams of America, I tear up. I can't help it," Stanley said.

She said the New Jersey senator had moved several slots up her list of presidential candidates. "But it's a long list," she joked.

Jerry Crawford, a Des Moines lawyer who is a leading Democratic Party power-broker, drove 150 miles to Muscatine Saturday to watch Booker. Then Crawford caught him again Monday afternoon in Urbandale, where the senator gave an energetic, hopeful stump speech to more than 500 people at an afternoon barbecue at his state headquarters.

Crawford, who backed Hillary Clinton in her successful run for the party's nomination in 2016, hasn't picked a candidate this time. But he said Booker is one of his favorites. "I think he has the strength and he has the right message," Crawford said, adding that Booker's positive outlook could catch hold as the caucuses draw closer.

Booker said in the interview that he realizes he's got a lot of work to do in Iowa. He vowed to return often and continue to build up his organization here. And he said he'll keep challenging voters to come together to heal the country.

Many of the problems Booker focuses on, including poverty,the environment and an unfair criminal justice system, go back for many years, he said. They can't all be blamed on Trump, he said, and they won't be magically solved by electing someone else.

"We need to be about more than just booting one guy from office," he said.