The battle over President Reagan's two most controversial judicial nominees is entering the final round.

After weeks of delay, the Senate Judiciary Committee is expected to vote today on the nomination of Jefferson Beauregard Sessions III to be a federal judge in Alabama. Senate Democrats are confident that the panel will not approve Sessions, who is accused of making racially insensitive remarks, such as characterizing the NAACP and American Civil Liberties Union as "un-American." Sessions, the U.S. attorney in Mobile, says his remarks were distorted or taken out of context.

But the Democrats and civil rights activists are unsure whether they can hold enough votes stop the GOP-controlled committee from sending the nomination to the Senate floor without a recommendation. The panel used that tactic last month to clear judicial nominee Daniel A. Manion after failing to approve him on a 9-to-9 tie.

Manion's nomination is expected to cause a fierce floor fight, perhaps next week. The former Indiana state senator, the son of the late conservative broadcaster and John Birch Society leader Clarence Manion, has been named to the U.S. 7th Circuit Court of Appeals in Chicago.

People for the American Way, the liberal lobby founded by producer Norman Lear, is attacking both nominations in a nationwide newspaper and radio campaign. "Daniel Manion and Jefferson Sessions are two prime examples of [Attorney General] Ed Meese's attempt to fill the courts with unqualified extremists," a newspaper ad says. A radio spot says that Manion has "never argued a federal appeal of any kind and never even had a legal article published."

But Manion has drawn strong support from Indiana's Republican senators, Dan Quayle and Richard G. Lugar. In a "Dear Colleague" letter, they said that some opponents "have given an inaccurate and misleading portrait of his record" and that "opposition to Dan Manion is based primarily on his conservative political beliefs."

"Part of the political case against Dan Manion can be reduced to this: guilt by association . . . Manion's critics accuse him of advocating all the views of his father . . . and the John Birch Society." The senators called these charges "mistaken and grossly unfair."

They also defended Manion's legal background in a small South Bend practice, saying the appeals court "ought not to be the exclusive preserve of academic scholars and lawyers with corporate practices in urban areas."