PORT HURON, Mich. — Giani DiTrapani was on his way out the door when his mom called out, “You better be voting for Trump!”

She shouldn’t have worried. Giani, then a high school senior about to vote in his first presidential election, had already lined up behind the outsider candidate, even getting into a Twitter war with a fellow student council member who was criticizing Trump.

In this small waterfront city where Giani grew up, going to church and voting Republican felt like a package deal he didn’t even have to think about, like the fries and a coke that come with a hamburger.

“Most of the people in my hometown are conservative,” Giani, now 21, said. “If you’re conservative, you’re Christian, and if you’re Christian, you’re conservative.”

His evangelical faith and conservative values were another way he bonded with his mom, Lucy Wisson, a fitness instructor who doted over her middle child and imagined he might go into politics one day.

But one jarring experience shortly after Trump’s election set off a chain of events that changed Giani’s political world forever, leaving Lucy reeling as her son transformed from a conservative activist into a vegan Alexandria Ocasio-Cortez fan in a little under a year.

“After that everything changed,” Lucy recalled.

Michigan State University was only a little more than 100 miles away from his hometown on the Canadian border, but Giani had been warned that making the trek to East Lansing would plunge him into an entirely different world.

“People would say, ‘oh, college is going to turn you liberal and indoctrinate you,’” Giani recalled. “I was, like, that’s not going to be true for me.”

Giani — determined to stay true to his conservative roots even as he became the first member of his family to graduate college — collected talking points from Fox News and conservative personality Tomi Lahren for use in debates with any liberals who wanted to challenge him.

Giani, petting his cat, now identifies with liberals on several key issues, a split from his conservative family. Erin Clark for The Boston Globe

“It’s frustrating because I can understand why they feel a certain way because I used to, too.” Giani DiTrapani

Soon after arriving on the sprawling campus, Giani joined the College Republicans and a newer Trump-supporting group called Turning Point USA. In his political science classes, Giani argued for stricter immigration controls, citing Fox News articles, and complained with fellow campus conservatives about how crazy it was that liberals wanted higher taxes.

Michigan By the numbers Compare to St. Clair County, Mich. How state voted in 2016 election 2012 election 2008 election Democrat Other Republican Democrat Other Republican Democrat Other Republican State voter turn out in 2016 election 2012 election 2008 election 63% 63% 66.2% Demographics: Population 9,925,568 75.50% White

13.70% Black

4.90% Hispanic/Latino

0.50% American Indian/Alaska native

2.90% Asian

0% Hawaiian/Pacific Islander

2.40% Two or more races Unemployment rate in June 2019: 4.20% Median income: $52,668 St. Clair County, Mich. By the numbers Compare to statewide How county voted in 2016 election 2012 election 2008 election Democrat Other Republican Democrat Other Republican Democrat Other Republican Demographics: Population 159,761 91.3% White

2.00% Black

3.20% Hispanic/Latino

0.10% American Indian/Alaska native

0.70% Asian

0% Hawaiian/Pacific Islander

2.40% Two or more races Unemployment rate in June 2019: 4.80% Median income: $53,641 Census data, Bureau of Labor Statistics, State of Michigan

Giani found his niche among campus conservatives. Yet, his worldview did not fit neatly into the Republican Party’s ideology. Unlike many GOP politicians, including Trump, Giani accepted that the climate is warming due to man-made carbon emissions, and he wanted the government to protect the environment. Giani is also gay, though his family didn’t know at the time, and was beginning to learn more about gay rights. But he didn’t believe his sexual orientation should affect his political orientation, given his main focus was economic policy — lower taxes and less regulation.

The clash between his environmentalism and conservatism came to a head in Florida that December, when Giani attended Turning Point USA’s national conference, along with thousands of other high school and college conservatives pumped for the Trump era. His mom gave him the money for the ticket — it was the first time Giani had flown on a commercial jet — and Turning Point comped the conference tickets.

On his first night in Florida, Giani ran into Ben Shapiro, the conservative commentator who started his career at the far-right Breitbart News Network, and shook his hand. “He’s the best debater ever and I’m meeting him, that’s so cool!” Giani remembered thinking.

The next day, Giani started feeling a bit uncomfortable. Shapiro gave a speech that encouraged the young conservatives to think critically about any president, including Trump. But Sebastian Gorka, Trump’s one-time adviser, spoke about Trump more as if he were an infallible being, or a god, who was above all criticism.

Then, in a break-out session after lunch, speaker Alex Epstein argued to a group of young conservatives that rising carbon dioxide emissions are ultimately good for the globe because they mean societies are advancing. Epstein passed out pins that proclaimed “I <3 fossil fuels.” Giani, who was flabbergasted at the presentation, expected some of his friends to be turned off, too. But his fellow Republicans were standing and cheering. “Is this what conservatives really think?” he recalled asking himself.

When Giani got back to campus, he unsubscribed from Turning Point USA’s videos on social media and stopped going to the college Republicans’ meetings. He also became a vegetarian — a stark change for the kid whose favorite snack foods were hot dogs and pizza rolls. He believed avoiding meat was one concrete way he could help the environment.

“The climate really changed my mind,” he said.

Giani returned to his hometown, a port city of about 30,000 people perched on the sky-blue Lake Huron, in the summer of 2018 and began working 80-hour weeks making sandwiches at Arby’s and Subway to save up money for college.

From behind the counter at Subway, Giani could see his hulking, glass-and-brick high school across the street, the same place his mom had gone to school. For the moment, mother and son were still living in harmony, even as their viewpoints began to diverge. Lucy, already a fitness nut, had embraced Giani’s vegetarianism and begun eating less meat herself as a way to be healthier. “I was proud of him,” she said.

Giani swam with his 10-year-old cousin, Averi Crisenbery, at a country club near his home. Erin Clark for The Boston Globe Gallery: Explore Michigan in photos

But Giani’s political evolution accelerated his sophomore year, making for a tenser summer this time around, when he moved back into the unpainted attic of his family’s modest home. Giani had transformed so quickly from a hotdog-loving committed conservative to an enthusiastic progressive vegan who supported the avowed Democratic socialist Congresswoman Ocasio-Cortez that his family’s heads were spinning.

Giani’s Uncle Scott argued with him over his Facebook posts featuring Senator Bernie Sanders and asked him incredulously if he planned to support “Pocahontas” — Trump’s nickname for Senator Elizabeth Warren — in the presidential election. (Giani replied that he was.)

“He’s beyond help,” his uncle joked.

Giani, an impassioned speaker who looks younger than his 21 years, has found the whole experience less amusing, as he fruitlessly endeavors to persuade his mom to support a Democrat in 2020, or at least not to vote for Trump again.

Their attempts to communicate across the political chasm that divides Americans echo the struggle playing out in many families ahead of the 2020 election, as personal bonds are tested by heated national political battles, and as Americans increasingly disagree about fundamental questions of what the country should look like.

“It’s frustrating because I can understand why they feel a certain way because I used to, too,” Giani said.

Abortion has been a particularly fraught subject. Giani, whose Christian faith is still paramount to him, struggled with the issue the most when rethinking his political positions, but eventually decided to support the right to an abortion. Lucy describes herself as “100 percent pro-life — no ifs ands or buts about it.”

Lucy, who is unfailingly upbeat and energetic, volunteers at a Port Huron pregnancy center that provides prenatal care and attempts to persuade women considering abortions to have the children instead.

“I don’t condemn anybody and I don’t want anyone to change because of what I’m doing,’’ said Lucy Wisson, who watched her son play in the pool with relatives on a sunny Saturday afternoon. Erin Clark for The Boston Globe

“President Trump is antipolitician — he’s just for America. . .I look at him sometimes as a pragmatist.” Lucy Wisson

“I’m totally into my Bibles,” Lucy, 51, said in their home one day this summer, while patting the closest copy of the holy book for emphasis. “I have every single version and I believe with all my heart how I should be, but I don’t condemn anybody and I don’t want anyone to change because of what I’m doing.”

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Lucy’s faith saw her through a harrowing period of her life after her abusive ex-husband left her with their five young children, when Giani was just 5 years old. She worked three part-time jobs, trying to survive. Sometimes she had to sneak her children into a back room in the hotel where she worked when no one in her family could watch them. She’d order the kids a pizza, turn on the TV, and pray it would work out.

A photo of Lucy Wisson, with her five children. After an abusive marriage, Wisson raised her children on her own. Erin Clark for The Boston Globe

“I just wanted my kids, that’s all I wanted,” Lucy says. “That’s why I believe what I believe so strongly because I know God can get us through anything.”

Lucy, who is now remarried, feels overwhelmed by what she sees as the rapid pace of change in American culture and even avoids watching TV because the ads and programming strike her as overly sexual compared to what she saw growing up. She’s turned off the TV in response to a Trojan condom ad and flinches in the grocery store if she hears people casually using profanity.

“I don’t want to know everything,” she explained. “I just want it to be like it was, you know?”

She supports Trump, especially when it comes to cracking down on illegal immigration and abortion, and she appreciates that he’s new to politics.

“President Trump is antipolitician — he’s just for America,” she said. “I look at him sometimes as a pragmatist.” That sentiment is the norm at her church and the small boat club where she teaches water aerobics. One of the boats parked there sports a “Trump 2020” flag.

For the most part, Lucy hasn’t lost her temper with Giani when he expresses his new political views or tries to change her mind. She’s even been convinced by Giani’s environmental arguments and says she wishes Republicans would become more environmentally conscious. But when Giani volunteered one day last June that he believed gender is a social construct and that people can locate themselves on a gender spectrum, she snapped. “Are you crazy?” she asked. “Are you a libtard?”

Giani DiTrapani left the Port Huron farmer's market with his mother, Lucy Wisson, front left, and sister Amara DiTrapani. Erin Clark for The Boston Globe

Giani backed down, but felt hurt. “I realized I can’t really say what I want to say,” he recalled.

But Lucy was going through her own painful transition as she dealt with both the shock and feelings of helplessness at seeing her son’s views shift so dramatically.

“I really thought, ‘what the heck is going on?’” Lucy recalled. “You went there and then you changed.”

The two also disagree about the recent impeachment inquiry into Trump. Giani believes the president should be removed from office over his request to foreign governments to investigate Joe Biden and his son, but Lucy said she believes the president had a good reason to do so. “I’m not letting it affect me,” she said.

There have also been good days, like when Lucy takes Giani to the Port Huron farmers market on Saturdays to stock up on microgreens and other veggies for his vegan sandwiches, and the day Giani convinced her that there should be laws preventing employers from firing people based on their sexual orientation.

“He won’t argue, and I appreciate that,” Lucy said. “He’s so calm!”

The differences between mother and son haven’t become barriers in their relationship, even now that Lucy knows about his sexuality. Lucy says he has opened her eyes to different issues.

“I love him for what he believes in no matter how different it is from us because he’s doing something on his own that I never did,” Lucy said. “I’m so proud of him.”

And for his part, Giani is bracing himself to accept his mom and other relatives when they will likely vote for Trump again in 2020.

“I still love them absolutely,” he said. “But sometimes I just have to change the conversation and say, ‘how was your day’ or something.”