In the 1980s, the Houston suburb of Pasadena was a Klu Klux Klan hotbed and the setting for honky-tonk action in the John Travolta film, Urban Cowboy.

Today it is reputed for its proximity to petrochemical plants, a spring festival that boasts the world’s largest strawberry shortcake, and for a political scene so racist that it attracted national attention in the wake of the US supreme court’s gutting of a key part of the Voting Rights Act.

Pasadena was one of the first places in the country to be placed back under federal supervision after that 2013 ruling. So Saturday’s mayoral and city council elections were keenly watched by civil rights advocates.

Those hoping Pasadena could stand as a beacon for the political power of Hispanic voters on a level playing field were left disappointed, as left-leaning and Latino candidates enjoyed only limited success.

With a couple of runoff elections to come, it looks unlikely that voters in the city of 154,000 will effect a change that overcomes establishment dominance to install a set of leaders that truly reflects Pasadena’s ethnic diversity.

“It’s going to be a series of steps, it’s not going to be a magic process, it’s going to take time,” said Oscar Del Toro, a defeated candidate who was born in Mexico. “If you want to accomplish something you have to start from the beginning. So this is at the beginning.”

He spoke as activists refreshed a giant television screen displaying the latest election results and consoled themselves with pizza at the local Democratic party headquarters, which are located in a strip mall on a busy highway in central Pasadena that acts as a symbolic dividing line.

The city is heavily segregated, with a Latino-dominated north side and a largely white south where more money has been spent on infrastructure and community facilities.

“It’s still a working class city, it’s just changed,” said Jennifer Halverson, Democratic president for the area. “Instead of a working-class white, Anglo city, it’s a working-class Hispanic city now. But the same people have been in power forever.

“They started suppressing at the local level so we’ve got to start winning back at the local level.”

They started suppressing at the local level so we’ve got to start winning back at the local level Jennifer Halverson

‘Racially polarised’

A demographic shift happening elsewhere in metropolitan Texas is especially pronounced in Pasadena, where a quarter of the population is foreign-born and the ethnic make-up has changed drastically in the past 30 years.

The city was once the location of a Klan bookstore, but by 2000 the numbers of white and Hispanic residents were roughly equal. By 2010, the city was 62% Hispanic and 33% white.

In 2011, the political map was reorganised to create eight city council districts. Latino candidates enjoyed success. Then came the 2013 supreme court ruling, Shelby County v Holder. It struck down a portion of the Voting Rights Act, meaning that states such as Texas with a history of discrimination no longer needed to obtain federal approval before changing their election rules.

The mayor of Pasadena, Johnny Isbell – who is white – promptly proposed changing the eight-district arrangement so two districts would become “at-large”. Such districts are elected citywide, rather than by voters in set neighbourhoods. Such positions are generally considered to give white candidates an advantage because turnout rates are typically highest among white voters.

The change was narrowly approved by city voters, even though an estimated 99.6% of Latinos were against it. Subsequent city council meetings did not lack drama. In March 2014 Isbell brought a gun to a redistricting hearing. The following month, he ordered police to eject a council member from the chamber when she went over the three-minute time limit while questioning whether the new system was legal.

The Mexican American Legal Defense and Educational Fund (Maldef) helped to bring a lawsuit, and in January this year a federal judge, Lee Rosenthal, blocked the move, saying its effect was to “dilute Latino voting strength” in a city with “racially polarised” elections. The city has appealed.

According to the judge’s summary of the city’s defence, Isbell’s “intent was only to mobilise Republican voters against Democrats, not Anglos against Latinos”.

Unconvinced, Rosenthal wrote in her decision: “Latinos were poised to elect a majority of the city council for the first time in the city’s history under the 8–0 map and plan.” She ordered Saturday’s elections to go back to the old eight-district method and for Pasadena to return to federal oversight.

Isbell, 78, was unable to stand as mayor again this year, because of term limits. But another white conservative, Jeff Wagner, is expected to win the runoff to replace him. The offices are officially nonpartisan, but activists at Democratic HQ on Saturday credited the results to a high level of Republican mobilisation and turnout, as a reaction to the attention on reform and talk of the potential for Latino gains.

“We do not see this in partisan terms,” Nina Perales, Maldef’s vice-president of litigation, said last week. “White folks have wanted to stay in power whether they were wearing a red T-shirt or a blue T-shirt, that’s just the way it is. And so what’s going on right now is largely a response to demographic change.”

Statewide, a federal judge has found that Texas’ voter ID law – which came into effect following the supreme court decision – discriminates against poor, Hispanic and African American voters.

This year, a panel of federal judges ruled that Texas redrew some congressional and state House district boundaries in 2011 with the intent of diluting the influence of minority voters. That legal fight is ongoing.

“We’re moving very, very slowly towards some kind of resolution now for the 2018 elections,” Perales said.