Pete Buttigieg's youth and optimism is winning over older Iowans Iowans who ABC News interviewed said they want a candidate who can defeat Trump.

Mixed in among the hundreds, sometimes thousands, of Iowans who attend a single Pete Buttigieg rally is an important voting bloc in the state that could help the South Bend, Indiana, mayor keep his momentum and produce a solid finish next year: older voters.

Young, intellectual, honest, authentic and disciplined are all terms those voters have used to describe Buttigieg at events during his most recent bus tour through northern Iowa.

The millennial candidate is tuning the message of his campaign to a vision towards the future, building on themes, such as, unity, belonging and to "launch the era that must come" after the Donald Trump presidency.

It's something that Iowa State University political science professor Steffen Schmidt said is winning over Generation X and baby boomers.

"I think the magic to his rise is he says, you know, we don't want to get into a big fight just for the purpose of a fight. The country's deeply divided. And I don't want to just get the nomination, I don't want to just become president, but I'd like to see if we can reduce the level of divisiveness," Schmidt said. "And that's selling very well."

Among registered Iowa Democratic voters, 82% of those 50 to 64 years old voted in 2016's general election and 85% of Iowans 65 and over turned out to caucus. That's 306,893 voters compared to the 100,226 votes cast by Iowans 18-34 years old.

Nationally, Buttigieg is among the top four Democratic presidential hopefuls, behind former Vice President Joe Biden and Sens. Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt., according to an ABC News/Washington Post poll that was released on Sunday.

But in a Quinnipiac University poll of likely Iowa Democratic caucus-goers released Wednesday, Buttigieg is in a statistical tie with those same candidates. Warren received 20% support, 19% for Buttigieg, 17% for Sanders and Biden at 15%, all within the +- 4.5% margin of error.

"I think he's gotten a lot of attention from Iowans, because he has a message of unity and kind of hope -- which is a stark juxtaposition to the president's message right now. So I think people who are wanting some sort of sanity back in the White House find a lot of comfort in Pete," Judy Downs, Executive Director of the Polk County Democrats said.

At a Buttigieg town hall in Waverly on Sunday, Mark Smith, 65, who lives in neighboring Fayette County, showed up with two candidates at the top of his list to caucus for on Feb. 3: Biden and Buttigieg.

Before the event began, Smith said the 37-year-old candidate intrigued him because of his youth and intellect. He said Biden, 76, doesn't have the ability to relay a message as clearly as Buttigieg does and Biden's age is a concern.

After Buttigieg finished his speech and answered questions from the audience, Smith said he was won over and his mind was made up.

"What I saw him give us right here is how he -- I think -- can change this country, how he can bring people together and inspire," Smith said. "Very, very pleased."

Among the ways Buttigieg naturally sets himself apart from other top-tier candidates is his age. Biden, Warren and Sanders are all in their 70's, while Buttigieg would be 39 years old on Inauguration Day.

A New York Times/Siena College poll released on Friday, shows Buttigieg only behind Biden when it comes to support from Iowa voters 65 and older.

Molly MacDonald, 78, said she's always liked the former vice president, but is leaning toward Buttigieg because she's hesitant to vote for someone close to her age.

"I know very well, you get up there, and you're just not as quick," she told ABC News at a town hall in her hometown of Algona on Monday.

Schmidt, who has been teaching at Iowa State University for 50 years, also said these voters tend to be more moderate, which is the lane Buttigieg seems to be driving in.

"They are worried about sort of off-the-chart candidates who just seem too explosive," he said. "When he talks about policy he talks about incrementalism and not blowing up the system. I think that appeals to a lot of those voters, many of them -- I would say -- have health insurance and, in some cases, are pretty happy with what they have."

Two of those voters who still have private insurance, but also Medicare, are Bob and Kathy Grant from Mason City. The 65-year-olds are retired but still work part-time. Bob Grant said Buttigieg is their top choice because he's a "young guy with a good train of thought."

They are still considering Warren, but said the downside to the Massachusetts senator, who Kathy Grant calls a "very sound thinker," who "doesn't mince words," is her $20.5 trillion "Medicare for All" plan that would force them to get rid of their private health care coverage.

"I don't think it will work. I think it's too expensive," she said, adding that they prefer Buttigieg's $1.5 trillion Medicare for All Who Want It plan, which would allow them to keep a private option.

The Grants and other Iowans who ABC News interviewed during the weekend did agree that they all want a candidate who can defeat President Donald Trump in the general election.

According to the Quinnipiac poll, 33% of likely Iowa Democratic caucus-goers are looking for "someone who can win the general election" and those who chose electability as the most important quality are split, with Biden, Buttigieg and Warren all at 21%.

The advantage Buttigieg has over those two older candidates, according to Schmidt, is that voters seem skeptical of electing another president in their 70's.

"A lot of them are saying, maybe the reason Trump is so erratic and kind of off the rails is his age," Schmidt said. "If that's the case, it makes the case for someone younger, who -- you know -- health wise and otherwise --- you know -- might be more appealing."