When Catherine Engelbrecht and her friends sat down and started talking politics several years ago, they soon agreed that talking wasn’t enough. They wanted to do more. So when the 2008 election came around, “about 50” of her friends volunteered to work at Houston’s polling places.

“What we saw shocked us,” she said. “There was no one checking IDs, judges would vote for people that asked for help. It was fraud, and we watched like deer in the headlights.”

Their shared experience, she says, created “True the Vote,” a citizen-based grassroots organization that began collecting publicly available voting data to prove that what they saw in their day at the polls was, indeed, happening -- and that it was happening everywhere.

“It was a true Tea Party moment,” she remembers.

Like most voter watchdog groups, she said, her group started small. They decided to investigate voting fraud in general, not just at the polling places, and at first they weren't even sure what to look for -- and where to look for it.

“The first thing we started to do was look at houses with more than six voters in them" Engelbrecht said, because those houses were the most likely to have fraudulent registrations attached to them. "Most voting districts had 1,800 if they were Republican and 2,400 of these houses if they were Democratic . . .

"But we came across one with 24,000, and that was where we started looking."

It was Houston's poorest and predominantly black district, which has led some to accuse the group of targeting poor black areas. But Engelbrecht rejects that, saying, "It had nothing to do with politics. It was just the numbers.”

The task was overwhelming. With 1.9 million voters and 886 voting precincts, Houston’s Harris County is the second largest county in the country -- and the key to Texas elections.

The group called for help and quickly got 30 donated computers and “tens of thousands of hours” of volunteer work. And then the questions started to arise.

“Vacant lots had several voters registered on them. An eight-bed halfway house had more than 40 voters registered at its address,” Engelbrecht said. “We then decided to look at who was registering the voters."

Their work paid off. Two weeks ago the Harris County voter registrar took their work and the findings of his own investigation and handed them over to both the Texas secretary of state’s office and the Harris County district attorney.

Most of the findings focused on a group called Houston Votes, a voter registration group headed by Sean Caddle, who also worked for the Service Employees International Union before coming to Houston. Among the findings were that only 1,793 of the 25,000 registrations the group submitted appeared to be valid.

The other registrations included one of a woman who registered six times in the same day; registrations of non-citizens; so many applications from one Houston Voters collector in one day that it was deemed to be beyond human capability; and 1,597 registrations that named the same person multiple times, often with different signatures.

Caddle told local newspapers that there “had been mistakes made,” and he said he had fired 30 workers for filing defective voter registration applications. He could not be reached for this article.

"The integrity of the voting rolls in Harris County, Texas, appears to be under an organized and systematic attack by the group operating under the name Houston Votes," the Harris voter registrar, Leo Vasquez, charged as he passed on the documentation to the district attorney. A spokesman for the DA's office declined to discuss the case. And a spokesman for Vasquez said that the DA has asked them to refrain from commenting on the case.

The outcome of the efforts grew in importance the day after Vasquez made his announcement. On the morning of Aug. 27, a three-alarm fire destroyed almost all of Harris County’s voting machines, throwing the upcoming Nov. 2 election into turmoil. While the cause wasn’t determined, the $40 million blaze, according to press reports, means election officials will be focused on creating a whole new voting system in six weeks. Just how they do it will determine how vulnerable the process becomes.

Editor's Note: An earlier version of this story misidentified Sean Caddle as Steve Caddle, and stated that he is currently an employee of the SEIU. Caddle is a former employee.