WASHINGTON - A candidate's drug arrest when he was 18 has riled up a Democratic primary contest for the right to challenge five-term Republican incumbent Pete Olson in a potentially competitive congressional district in Houston's southern suburbs.

Sri Preston Kulkarni, a leading labor-backed candidate in the five-way March 6 Democratic primary, acknowledged Tuesday that he was arrested for less than a gram of cocaine when he was a teenager in 1997. The felony charge was later dismissed by a Harris County judge after a two-year probationary sentence, a disposition known as "deferred adjudication" that is frequently meted out for first-time drug offenses.

Kulkarni, now a 39-year-old ex-foreign service officer and one-time Senate aide, described the incident as a youthful indiscretion at a stressful time in his life when his father was terminally ill with cancer.

"We should not be stigmatizing our youth for the rest of their lives," he said.

EDITORIAL BOARD PICKS: Aronoff, Siegel or Walker, Kulkarni and Steele

Nevertheless, the allegation, made at the start of early voting in Texas, has shaken up a U.S. House race in which Democrats hope to make inroads in their quest to loosen the Republican Party's long grip on the state.

Kulkarni disclosed the arrest to the Chronicle on Tuesday after the case was raised by the Fort Bend County Chapter leader of Our Revolution, a group representing a progressive coalition of activists who supported the 2016 presidential campaign of Vermont Sen. Bernie Sanders.

Doug Beaton, the leader of the chapter, warned Fort Bend County Democratic officials on Kulkarni's previously undisclosed past in a letter posted Monday on social media. The letter suggested that Kulkarni, whose full first name is Srivinas, is running under an assumed name and that he had previously registered with the Federal Election Commission to run for a congressional seat in Massachusetts.

"As these concerns have been validated, we feel that this candidate would be a considerable liability for the Democratic Party in the midterm elections," Beaton wrote.

Kulkarni said neither charge is true.

As the mixed-race child of East Indian ancestry, there are several variations on his name, including Srinivas Rao Kulkarni, the name under which he was adjudicated on the drug charge in 1997. His full name is Srivinas Rao Preston Kulkarni. Preston is his mother's maiden name.

He said the accusation that he first filed to run for Congress in another state stems from a "computer glitch" that abbreviated the state of the 22nd Congressional District as "MA" for Massachusetts, instead of "TX" for Texas in his December filing.

The error was corrected in a new filing on Dec. 20, listing his address in Pearland, inside the lines of the gerrymandered suburban district.

Working in overseas posts

The discrepancies, however, have been used to raise doubts about Kulkarni's ties to Fort Bend or Brazoria County, as distinct from Houston, where he was raised as a child before heading off to the University of Texas and then a career as a foreign service officer in the State Department.

Fueling those doubts is Kulkarni's long overseas career, which took him to Iraq, Israel, Russia, Taiwan and Jamaica. While his critics note that he did not appear to have ever voted in Texas, he said he voted by absentee ballot from Iraq in 2008 and from Israel in 2012.

In 2016, he acknowledges he voted in Massachusetts because he was there working on a master's degree in public administration from Harvard's Kennedy School.

Beaton, in an interview Tuesday, said those concerns are more important than Kulkarni's drug arrest, which he sees as a youthful mistake. "To me the idea is that we want to put the best candidate forward after the primaries, with the best chance of beating Pete Olson in the November elections," he said. "There is nothing personal in this."

Fort Bend County Democratic Party Chairwoman Cynthia Ginyard said she saw Beaton's letter but declined comment. "We cannot speak for or against one of our candidates in the primary," she said.

But the county's past Democratic chair, Don Bankston, a member of the party's state executive committee, said the attack on Kulkarni is off base and potentially slanderous.

"It's a defamatory lie," said Bankston, who supports Kulkarni in the primary. He noted that Beaton's letter accused Kulkarni of a "felony conviction for possession."

Critic admits "felony' wrong

In fact, the case was dismissed without a conviction after Kulkarni completed probation and paid a $500 fine. He noted that he was able to obtain a top-secret security clearance at the State Department.

Beaton acknowledged the legal distinction, saying "I wish I had phrased that differently."

Kulkarni's backers say there was no intent to run from his past. Federal law allows candidates to run under known nicknames that clearly identify them. Some examples: Jeb Bush, whose real name is John Ellis Bush, and Beto O'Rourke, whose full legal name is Robert Francis O'Rourke.

Beaton's group, Our Revolution, decided to back health care advocate Steve Brown in the Democratic primary that features two top fundraisers: Letitia Plummer, a dentist who had pulled about $70,000 by the start of the year, and Kulkarni, who hauled in more than $41,000.

Brown, meanwhile, reported a little more than $11,000 in receipts. Business executive Mark Gibson, following at 2016 bid in which he won 40 percent of the vote against Olson, has raised more than $13,000.

All sides say the stakes are high. Although the district has long been a GOP stronghold, Hillary Clinton carried increasingly diverse Fort Bend County in 2016, raising Democrats' hopes for 2018.