DALLAS (AP) — Rep. Eddie Bernice Johnson has been an outspoken voice for two decades as the first black woman to represent North Texas in Congress.

Now, she faces serious opposition in the May 29 primary election, and the effort to unseat her is just one of several challenges against some of the longest-serving black members of Congress.

“I will always be ever more grateful for the trails that she has blazed,” said Eva Jones, owner of a barbeque restaurant who was chairwoman of Johnson’s first House campaign in 1992. But “there has come a time where we need new leadership, like in any business, like with anything.”

Longtime black incumbents in Dallas, Detroit and New York City are being challenged by a younger generation of black office-seekers who aren’t waiting for retirements by the old guard, including nationally known figures whose activism dates to the civil rights movement.

In Michigan, several people are challenging 82-year-old Rep. John Conyers, the oldest black member of the House.

One of his rivals, Michigan state Sen. Bert Johnson, said people who have voted for the congressman for decades in his Detroit district recognize that “perhaps we’re not trying to integrate lunch counters so much” as work to prevent foreclosures in struggling neighborhoods.”

“Those people know that there is a nexus between their experience and the youthful vigor and zeal that I bring to the table,” said Johnson, who at 38 was born eight years after Conyers took office in 1965 following his work with civil rights leaders Martin Luther King Jr. and Rosa Parks.

Eddie Bernice Johnson’s two challengers are careful not to criticize her directly, but say they hear increasing doubts from voters in south Dallas, where neighborhoods have struggled long before the recession.

“North Texas has seen a lot of economic growth. Unfortunately, this district and our community hasn’t really shared in that economic development,” said Taj Clayton, one of the congresswoman’s opponents.

Johnson, 76, grew up in Waco, Texas and moved to Dallas where she worked as a nurse. She decided to get into politics after a trip to buy a new hat at a shopping mall.

“I learned in just a very stark shock that I could not try the hat on,” she told the Dallas Morning News in 1987. “I never experienced that in Waco. We could try on clothes. I found that black women (in Dallas) could not try on shoes. People tried them on for you, or they would measure your foot and guess your size.”

She didn’t buy the hat. Instead, she organized a boycott and took her first step into politics. More than a decade later, local leaders encouraged her to run for Texas state representative, and she won.

In 1986, she was elected to the state Senate. Six years later, she ran for the U.S. House from a district she helped draw as a state senator.

She’s won 100 percent of the vote in every primary since. Johnson, who declined to be interviewed for this report, has won federal funding for new mass transit and other local projects. She’s also fought against a Republican-backed voter ID law that she says would disenfranchise minority voters.

Supporters said the congresswoman’s experience is needed in her district.

“This election is too important … to hand everything to a novice that’s going to help shape the policies for (President Barack Obama’s) second term,” said David Henderson Jr., a pastor and president of the Baptist Ministers Conference of Dallas. “We need someone with her stature, with her status.”

One of Johnson’s challengers, Texas state Rep. Barbara Mallory Caraway, worked for Johnson when she was a state senator before Johnson fired her. Caraway, 56, is married to a Dallas city councilman and is well-known for defeating incumbents in two previous races. She spends much of every day walking the district to talk to voters.

“Twenty years is a long time to be in one elected office. Now’s the time. It’s time for new leadership,” Caraway said.

Clayton, 35, the second of Eddie Bernice Johnson’s challengers, is a Harvard-educated lawyer and son of local glass factory workers. His campaign staff includes a former national field director for Obama’s 2008 campaign.

Redistricting has expanded the district into majority Latino areas where voters are less familiar with all three candidates. The primary is also being held later than expected, on the day after Memorial Day, which could affect turnout.

Johnson has not debated her opponents and has held relatively few campaign events. She dismissed both in a radio interview last month.

“If you want to know my honest opinion, I don’t think anybody who’s running against me is ready to come to this job,” Johnson said.

She has a coveted endorsement from Obama, who rarely intervenes in Democratic primaries. Johnson’s campaign says she remains focused on the district by holding weekend events and working hard in Washington during the week.

“The way she has always approached it is, ‘I’ll run on my record, so the best thing I can do is continue to extend my record,’” spokesman Eddie Reeves said.

Johnson is a former chairwoman of the Congressional Black Caucus, an influential group that once counted Obama as a member. She’s one of the oldest members of the CBC, which has at least two other members in tough re-election fights — Conyers and New York Rep. Charles Rangel, 81, who has been a political mainstay in Harlem since 1971.

Rangel, convicted on House ethics charges in 2010, faces two black Democrats in his bid for a 22nd term — local district leader Joyce Johnson and former Democratic National Committee official Clyde Williams, as well as Latino state Sen. Adriano Espaillat. Latinos make up more than half the population in Rangel’s newly redrawn district.

Copyright 2012 The Associated Press.