Brent Welder, a Democrat running for Congress in the Kansas City suburbs, addresses volunteers at his campaign office on July 3. (David Weigel/The Washington Post)

— Brent Welder walked into his campaign office to share the good news. Ever since Alexandria Ocasio-Cortez’s upset victory in a Democratic House primary in New York, he’d been deluged with calls. He’d been endorsed by Sen. Bernie Sanders (I-Vt.), and by Ocasio-Cortez herself. He’d raised tens of thousands of dollars from liberals looking for their next cause, and finding it in the suburbs of Kansas City, with a candidate running proudly on “Medicare for all” and a $15 minimum wage.

“People keep asking, are these the kind of ideas that a candidate can talk about and be successful in Kansas?” said Welder, a 37-year-old labor lawyer. “What I’ve learned on this campaign is that the only way we can be successful is by talking about these ideas.”

Welder, whom local Democrats see as one of the front-runners in a crowded congressional race, is one of many candidates urging his party to scrap the centrist talk that defined its last successful takeover of the House in 2006 and turn decidedly left.

Shortly after her win, Ocasio-Cortez went on MSNBC to say that Welder was running “the exact same race” that she did.

Ocasio-Cortez, who became a national Democratic star after her victory, has endorsed a number of candidates with messages just like Welder’s — Justice Democrats, committed to abolishing the federal immigration agency ICE, passing universal Medicare, and making college tuition-free.

She also has extended her reach beyond the Bronx. Last week, she held a New York fundraiser for Abdul El-Sayed, a Democrat running for governor of Michigan. This month, she will campaign alongside El-Sayed and Welder in their home states.

Kansas’s 3rd Congressional District is the only one in the Great Plains that backed Hillary Clinton for president, but it is far from a liberal outpost. For 12 years, it sent centrist Democrat Dennis Moore to Congress; Rep. Kevin Yoder, elected in the red wave of 2010, is the first antiabortion Republican to hold it for more than one term.

The six Democrats fighting for the seat are running to Moore’s left, trying to redirect the pulsating energy of the national Trump resistance into a red-state campaign with a message far bolder on health care, immigration, and gun rights than Moore’s was.

Welder, a former Sanders delegate who has gotten the most attention among the Democratic candidates, sees his approach as energizing the party’s base and at the same time attracting populist voters who sided with Trump. The pitch: What’s good for the Bronx and Queens would be even better for Kansas.

“I haven’t sat down and had a deep policy discussion with Alexandria, but whether a person lives in New York or Kansas City, they want the same things,” Welder said. “They want the health-care system fixed. They don’t like poverty. They don’t like corruption. If you want to tell me that she lives in the one district where people want that agenda, why did Bernie Sanders win Kansas by a 2-1 margin?”

Republicans, however, recall that although Sanders won the state’s presidential caucuses, Trump won the general election. Although unsure who has the advantage in Welder’s six-way primary, they’re eager to point out that he moved to the district, where his wife was born, just last year. They’re also optimistic that he has moved the rest of his rivals to the left.

“I’ll be the moderate in this race in the fall,” Yoder said in an interview. “This is a center-right district, and people from time to time will cross over to vote for a Democrat. When they worry that the Democratic Party is being taken over by folks who describe themselves as ‘democratic socialists,’ they’re not going to take that risk.”

At the start of 2017, Kansas’s 3rd District looked like one of the country’s most promising Democratic targets. In addition to Clinton’s victory in the district, Democrats also picked up 16 seats in the state legislature, many of them in the Kansas City area — the biggest such swing toward the party anywhere in the country, powered by voter anger at Republican Gov. Sam Brownback’s deep tax cuts and their effect on schools.

“People in Kansas realized that the Brownback tax experiment was a complete disaster that almost ruined our state and our schools,” said Jerry Stogsdill, a Democrat who flipped a traditionally Republican state House district that covers Prairie Village. It was education, he said, that moved votes — not national politics.

Yoder, however, has been stacking up money — $2.2 million for the election cycle — and building a grass-roots campaign team of 75 student volunteers, who by this month were knocking on 29,000 doors per week. But for the first time in his career, he said, he expects the race to come down to single digits.

“The Democrats have a spigot of energy that they can just turn on,” Yoder said. “I know they do, because I saw that same spigot in 2010, on our side.”

Yoder and other Republicans hoped that Democrats would make their path more difficult by tacking hard to the left — a hope that grew after Ocasio-Cortez’s victory. In a new Washington Post-Schar School poll, conducted from June 27 through July 2, voters in key “battleground” House districts viewed the president negatively, with just 42 percent approving of his performance. Seventy-two percent of battleground district voters said they were bothered “by photos and stories about children being separated from their parents” by immigration enforcement.

Yet while those voters said that they trusted Democrats on immigration, Trump enjoyed a 17-point lead on the question of border security, and a 16-point lead on “ensuring immigration does not hurt American workers” — an indication of potential Democratic difficulty ahead.

“This is a largely suburban, center-right district,” said Kris Kobach, a conservative Republican running for governor who lost a 2004 race against Moore. “It’s not a district where you can run hard to the left, take quasi-socialist policies to voters, and say: ‘Hey, get behind me on this.’ The notion that Americans don’t want immigration laws enforced is simply ridiculous.”

Over the Fourth of July holiday, the problem in translating a Bronx agenda into the heartland was evident as the candidates met voters in the blistering heat. As they watched Democrats march by in Lenexa’s annual parade, a trio of women who lived at a nearby retirement home recalled voting for Moore but worried about the ideas coming from today’s Democrats. Expanding Medicare, they said, meant less coverage for them. Abolishing Immigration and Customs Enforcement, they said, would mean no immigration enforcement whatsoever.

“Can you imagine if they got rid of that?” asked Carol Paramore, 80. “It wouldn’t be safe. You wouldn’t be able to sit here and watch a parade.”

None of this year’s Democrats — not even Welder — have called for the abolition of ICE, although other party figures have taken that stance. Welder said he had not reviewed pending legislation that would scrap ICE, and said he wanted a “serious restructuring of immigration policy” to prevent family separation.

Democrats remain hopeful that they can cut through the noise on each liberal issue — and that voters will let them.

As she canvassed neighborhoods near Lenexa this week, one of the Democratic candidates, Sylvia Williams, argued that her business background gave her license to talk about “Medicare for all” as a cost-saving issue, rather than as part of an overtly liberal agenda. The voters she met at the doors did not name any litmus tests, she said, preferring only to cast a ballot for someone who could beat Yoder.

“I just don’t like the direction the Republican Party has taken,” said Adam Iseman, 35, after taking a brochure from Williams.

But Republican voters are paying close attention to the Democrats’ new issues — and are ready to paint the party as out of touch.

“I’m from Kansas City, Kansas, which was invaded by illegals in 1993,” said Michael Kalny, 65, a Republican precinct committeeman in the city of Shawnee. “Go see what type of community you’ve got there now — all Hispanic. That’s just one city. It’s happening across the country.”