DALLAS, Texas -

A previously unreported 2010 state raid of a Houston effort to register low-income voters is raising concerns from critics that the Republican favorite to become the next governor of Texas used his post to suppress voter registration efforts that could favor Democrats.

In 2010, armed investigators dispatched by the office of Texas Attorney General Greg Abbott and suspecting election fraud raided the headquarters of a voter registration group called Houston Votes. A year later, the investigation was closed with no charges filed. But Houston Votes never recovered, the Dallas Morning News reported Sunday.

Fred Lewis, president of Texans Together, the nonprofit parent group of Houston Votes, said the raid was over the top: "They could have used a subpoena. They could have called us and asked for the records. They didn't need guns."

Now running for governor, Abbott declined to comment on the case. But his aides said the raid was part of an effort to preserve the integrity of Texas elections.

Still, some critics contend that it and other efforts are part of an official, partisan plan to suppress voters who don't support Republicans.

The 2010 Houston Votes raid coincided with Lewis' testimony in the trial of former U.S. House Majority Leader Tom DeLay. Lewis had filed a complaint against DeLay that helped lead to his indictment on corruption charges.

Abbott spokesman Jerry Strickland didn't recall being briefed by staff members on the Houston Votes investigation.

"In this investigation — and all other investigations conducted by the Office of the Attorney General — evidence uncovered dictates direction," Strickland told the Morning News via email. "To insinuate there were other factors at work in this case is ludicrous and unfounded."

Texas is undergoing a dramatic demographic shift. A Rice University study of census data found that between 2000 and 2010, the Houston metropolitan area added 1.2 million people — more than any other urban region in the U.S.

Nearly 70 percent of the residents of Harris County, which includes Houston, are Hispanic, black or Asian. Those groups are driving population growth.

Meanwhile, Republican candidates for governor have gone from comfortably carrying Harris County to narrowly losing it, beginning with the 2010 election.

Abbott's 12-year record as attorney general has featured many disputes over voting rights issues. Republicans have tightened controls on voter registration efforts, and required that voters show photo identification at the polls — saying they want to combat electoral fraud.

As the state's top lawyer, Abbott has defended such efforts. But Democratic critics say some of those policies could amount to vote-suppression.

The Houston Votes case is not the only one of its kind, though it's unclear how often Abbott's office investigates allegations similar to those levied against the group. In response to requests from The News, the attorney general's office provided a list of 637 potential violations of the Elections Code referred to Abbott since he took office in late 2002.

Strickland said he could not say how many were investigated or how many involved alleged voter registration fraud.