AMNA NAWAZ: Two weeks ago, many parts of the country saw dramatic political shifts to the right.

Even places that were once considered Democratic strongholds flipped red.

Special correspondent Christopher Booker traveled to one such area, near the southern border of Texas, and has this report.

JORGE BAZAN, Starr County, Texas, Resident: Good neighbors, people tend to look for each other.

CHRISTOPHER BOOKER: Fifty-six-year-old Jorge Bazan has lived in the Rio Grande Valley just minutes from the southern border his entire life.

And for as long as he can remember, Bazan and his family voted for Democrats.

JORGE BAZAN: They used to tell us the Democratic Party would help out the poor.

Clinton was an awesome president.

I voted for him twice.

Obama, I voted for him twice.

I think they did a good job.

CHRISTOPHER BOOKER: But Bazan, who works for a local water utility, says Democrats have abandoned the working class.

JORGE BAZAN: They say they haven't, but I think they have.

CHRISTOPHER BOOKER: So, in 2016, Bazan voted for Donald Trump.

He went for him again in 2020 and this year.

JORGE BAZAN: This time around, it was easier than the prior elections.

People in this area are hurting due to the economy.

We used to buy three combos at Whataburger for $20.

It would feed the family, my family.

Now I pay $24 for two.

CHRISTOPHER BOOKER: Bazan's shift is part of a much larger trend now coming into focus.

Look at this map from 1996, when President Bill Clinton won all but two counties along the Texas border.

Fast-forward to this year, the map has nearly flipped.

Perhaps no county has gotten more attention than Starr.

In 2016, it voted almost 80 percent for Hillary Clinton.

In 2020, President Biden still won, but only by five points.

This year, former President Trump won Starr county by 16 points, turning it red for the first time in over 120 years.

Depending who you ask, the flip was either stunning or predictable.

Starr County is 97 percent Hispanic, the highest in the country.

It's also largely Catholic and among the poorest counties in the U.S., with a household median income of just under $36,000.

At the Texas cafe, a Starr County staple for almost a century, diners don't shy away from politics.

There are pictures of John F. Kennedy on the wall, but these days there's a different tone.

JOSIE AMADOR, Starr County, Texas, Resident: I was a Democrat all my life, but then, when things started getting -- like, the economy and things like -- I said, I'm voting Republican, see if we can see a change in our system.

MARLENE GARZA, Starr County, Texas, Resident: I like Trump because when he was president the first time, everything was a lot more economic, the gas, the food, everything.

CHRISTOPHER BOOKER: Many also support Trump's promises on immigration, including mass deportations.

But others now wonder about the consequences.

ANDY HERNANDEZ, Starr County, Texas, Resident: Even though we voted for him, how far is he going to go?

If you came yesterday, I'm not going to fight for you, but I will fight for you if you're here -- like, if your roots are here, you have a house, you have got your family, you have got your kids in school.

ROSS BARRERA, Former Chair, Starr County, Texas, Republican Party: Hey, how do I join?

I want to.

I'm a Republican.

CHRISTOPHER BOOKER: Ross Barrera is the former head of the Starr County GOP.

He too has some concerns about how the deportation process might unfold, but he says we have a law.

There are a lot of people wondering, how does a Latino population vote for someone who is advocating for mass deportation like this?

ROSS BARRERA: Well, because we don't see ourselves as Latinos.

We see ourselves as Americans.

And as long as the national media or anybody keeps saying, you're Mexican American, no, I'm an American of Mexican descent.

Come here the legal way like our ancestors did.

As an officer, you command.

You lead.

CHRISTOPHER BOOKER: Barrera is a retired Army colonel born and raised here.

His parents supported Ronald Reagan in the 1980s, so he did too.

But in Starr County, they were outliers.

ROSS BARRERA: I think the Democrat Party at one time was the party of the working class, and they focus on that.

They focus on the family.

We want you to have some type of assistance to go to college or we're going to help you getting your first house.

Here, we call those Blue Dog Democrats.

They don't exist anymore.

The message that the Democrats had were social issues.

I got it.

Yes, I got that.

But that's not what's hurting people here.

CHRISTOPHER BOOKER: Despite many downballot wins, Democrats here are trying to figure out what went wrong in the presidential race.

JESSICA VERA-RIOS, Chair, Starr County, Texas, Democratic Party: No one really has come from the Democratic Party to visit.

They just felt that this area was blue maybe.

CHRISTOPHER BOOKER: That it was a lock.

JESSICA VERA-RIOS: And it was turnkey.

But it didn't.

CHRISTOPHER BOOKER: Jessica Vera-Rios leads the Democratic Party of Starr County.

She says one thing seems obvious.

JESSICA VERA-RIOS: Trump did an excellent job of running a campaign, of selling a propaganda.

CHRISTOPHER BOOKER: Is the Democratic Party losing the information battle then?

JESSICA VERA-RIOS: Yes, I do believe that.

There was a Republican commercial coming on talking about transgender issues, sexuality, and they were selling it.

And that's when I thought, hmm, we may have problems.

CHRISTOPHER BOOKER: Even though Vice President Harris didn't explicitly campaign on transgender rights, people we spoke with felt those Republican attacks resonated.

CECILIA HERNANDEZ, Starr County, Texas, Resident: he Democratic Party was on the defense.

CHRISTOPHER BOOKER: Cecilia Hernandez's family owns a garbage collection company.

They're Democrats and put Harris signs outside their business.

But as the election neared, the signs were vandalized.

And a note left on their door said: "This is a Republican state.

Go back to Mexico."

CECILIA HERNANDEZ: I think that they wanted to intimidate us and they wanted to scare us.

CHRISTOPHER BOOKER: Hernandez was surprised Starr County flipped as dramatically as it did.

She thinks Democratic economic policies are more helpful to valley residents.

But she says: CECILIA HERNANDEZ: We don't do an effective job of communicating that.

I think the fearmongering on the other side, all the misinformation did not help us at all.

Half the things that people were saying, I was just like, I'm not on the same planet as these people.

CHRISTOPHER BOOKER: Still, despite the loss, Hernandez thinks legitimate civil competition between two political parties is ultimately better for this area.

ALVARO CORRAL, University of Texas, Rio Grande Valley: South Texas and the Rio Grande Valley is moving probably at the very least in the purple direction.

CHRISTOPHER BOOKER: Alvaro Corral is a political scientist at the University of Texas, Rio Grande Valley.

He says this year's results should be a warning sign for Democrats.

ALVARO CORRAL: The growing racial and ethnic diversification of America, led by Latino Hispanic voters and the electorate, was thought to be a boon for Democrats moving forward and a way for them to sort of lock their hold in national politics.

But as we have seen with the Rio Grande Valley and its shifts, potentially, that story is too simplistic and that demographics aren't necessarily destiny.

It turns out that you need to ask for people's votes.

You need to deliver policy.

You need to deliver policy in big ways that resonate with people's pocketbooks.

And if you don't do that, you may be surprised by what you get.

CHRISTOPHER BOOKER: In Starr County, Trump's win has raised more questions than answers.

Will his tariff and tax proposals actually improve the economy?

How will an immigration crackdown impact the community?

And, even longer term, has this once deep blue area finally turned red?

For the "PBS News Hour," I'm Christopher Booker in South Texas.