WASHINGTON — As Senator Thad Cochran, the veteran Republican, fights for his political life in Mississippi by taking the unexpected step of courting black Democrats, conservative organizations working to defeat him are planning to deploy poll watchers to monitor his campaign’s turnout operation in Tuesday’s runoff election.

Kenneth T. Cuccinelli II, president of the Senate Conservatives Fund, a political action committee that has spent hundreds of thousands of dollars backing Mr. Cochran’s Tea Party opponent, State Senator Chris McDaniel, said in an interview on Sunday that his group was joining with Freedom Works and the Tea Party Patriots in a “voter integrity project” in Mississippi.

The groups will deploy observers in areas where Mr. Cochran is recruiting Democrats, Mr. Cuccinelli said. J. Christian Adams, a former Justice Department official and conservative commentator who said he was advising the effort, described the watchers as “election observers,” mostly Mississippi residents, who will be trained to “observe whether the law is being followed.”

After nearly 42 years in Washington, Mr. Cochran is facing a dire political threat from Mr. McDaniel, a former radio talk show host. Under state elections law, Democrats may vote in the runoff if they did not vote in the Democratic primary on June 3.