After years of going after some of the biggest names in Texas politics, District Attorney Ronnie Earle (search) reckoned 2004 would be the year he would retire.

Then Earle found himself in charge of a campaign-finance investigation that has set off tremors from Austin to Washington. Calling it the most important investigation of his nearly 30-year career as D.A., the Democrat decided to stay on, and got himself re-elected in November to another four-year term.

That, of course, may have set off even more tremors.

So far, Earle's two-year-old probe has led to the indictment of three associates of Republican U.S. House Majority Leader Tom DeLay (search) of Texas and eight corporations. It also has stirred rampant speculation at the state Capitol over who among the legislators might be next.

The district attorney suspects a political action committee set up by DeLay was used to funnel $2.5 million in illegal corporate contributions to Republican candidates to help the GOP win control of the Texas House in 2002 for the first time since Reconstruction (search). (The GOP later used its majority to redraw Texas' congressional districts to favor Republican candidates.)

Texas law prohibits the use of corporate money for political activity.

"I think that democracy is at stake," said the 62-year-old Earle, who has been D.A. since 1977. "The issue is whether large corporate interests can buy more democracy. If large monied interests can control elections, then the principle of 'one person, one vote' is meaningless."

Attorneys for the defendants have said their clients did not knowingly break any law, and have noted that state law does allow corporate money to be used for administrative expenses. It is defense Earle contends is flawed.

"Everybody knows what administrative expenses are - rent, utilities, overhead of that sort. It is a perversion of the law to try to stretch that to include expenses that are clearly designed, that are clearly political," he said.

Earle has been repeatedly accused by Republicans of conducting a partisan witch hunt. U.S. Rep. Henry Bonilla (search) recently referred to Earle as a "partisan, crackpot district attorney." A spokesman for DeLay has charged that Earle is more interested in "self-promotion than promotion of justice."

Earle is quick to point out that, over the years, he has investigated four times as many Democrats as Republicans, including some friends. He has even filed charges against himself for missing the campaign finance reporting deadline by a day.

"This job, your duty, is not to your friends. Your duty is to the law," Earle said. "I don't know what my reputation is. I know what the results are. I know what the numbers show. Sometimes you lose, but you always try."

The Democrats prosecuted by Earle and his Public Integrity Unit (search) include former Texas House Speaker Gib Lewis, former Texas Attorney General Jim Mattox, former State Treasurer Warren Harding and former Texas Supreme Court Justice Don Yarbrough.

In 1994, Earle brought charges of official misconduct and record-tampering against Republican U.S. Sen. Kay Bailey Hutchison, but dropped the case during the trial.

Lewis, who was friendly with Earle, pleaded no contest to charges he failed to disclose a business investment in 1992. Lewis was fined $2,000 and retired soon after.

Mattox was acquitted on bribery charges brought by Earle.

"You might question his competence as district attorney, but I don't think you could question his motivations as being overly partisan about the matter," Mattox said.

As part of the campaign-finance investigation, Earle has subpoenaed the records of Republican Texas House Speaker Tom Craddick and other lawmakers. So far, no legislators have been charged. But the ramifications of the case could be far-reaching.

"Anytime you are messing in the business of the U.S. House majority leader, you're playing on a big stage," said Ross Ramsey, publisher of Texas Weekly, an online newsletter on politics.