SACRAMENTO, California (AP) — Anger around a 30-year-old religious clash in India that left thousands dead has crept into one of the closest and most expensive congressional races in the United States.

Some Sikh political activists and the California Republican Party are campaigning against Democratic Rep. Ami Bera, saying he refuses to acknowledge the alleged involvement of the Indian government in the anti-Sikh rioting in 1984.

Bera, a physician, is the only Indian-American in Congress.

Other Sikh leaders are planning a fundraiser for Bera this weekend, dismissing the opposition as a fringe group that doesn't represent their religious community. They praise Bera, a Unitarian who was raised Hindu by Indian immigrant parents, as a valuable advocate for all South Asians.

Sikhism is a monotheistic religion with roots in modern-day Punjab that emphasizes equality and good works. Male followers often wear turbans. In California, Sikhs have a long history as farmers in the Central Valley.

Bera's 7th Congressional District, which is about evenly divided between Democrats and Republicans, has about 6,000 registered voters of Indian descent, according to Political Data Inc., a California firm that provides detailed breakdowns of voting districts.

The race between Bera and Republican Doug Ose, a former congressman, has attracted more than $4 million from outside interest groups. The margin of victory in November is expected to be razor-thin, so even a small-scale revolt from within a single ethnic community could help tilt the election.

A group of activists calling itself American Sikhs for Truth plans to send 1,500 anti-Bera mailers in English and Punjabi to Sikh households and to deploy volunteers on the streets in the coming days.

The massacre of Sikhs marks one of the darkest periods of sectarian violence in recent Indian history. After violently suppressing a Sikh insurgency and an army attack on the holiest Sikh site, Prime Minister Indira Gandhi was assassinated by her Sikh bodyguards in 1984.

Her killing prompted anti-Sikh rioting across northern states that left more than 3,000 people dead, some hacked to death and others burned alive. Government officials have been accused of inciting then ignoring the violence.

Ahead of the clash's anniversary in November, a group of Sikhs asked congressional candidates in Northern California whether the deaths happened with government assistance or lack of intervention, and if they would pursue justice for the victims' families. Bera's campaign was among nine that did not answer the questions.

In a prepared statement to The Associated Press, Bera called the killings a tragedy and said he is "hopeful that the Indian government has learned from the past."

Voters who are critical of his stance say Bera is bending to pressure not to offend prominent Indian-American campaign donors in America or the government of India.

Most Sikhs in the U.S. care more about domestic policy than foreign policy and "homeland politics," said Karthick Ramakrishnan, a political science professor at the University of California, Riverside and director of the National Asian American Survey.