Oprah Winfrey’s decision not merely to back Barack Obama but to go out and shill for him in the early voting states is a risky strategy for America’s top woman entertainer. Endorsing a politician, not least one who might lose, is a gambit few show business agents would recommend to their clients because things can go wrong so easily. Perfectly decent acting and singing careers have been wrecked on the shores of political activism.

Ms. Winfrey seems oblivious to the dangers of tying herself to Mr. Obama’s mast. “This is what I know I am supposed to be doing. I feel compelled to do this,” she told Diane Sawyer. And personal appearances are just the beginning. Next week, her company Harpo Films will release a movie, “The Great Debaters,” destined to give Mr. Obama an extra boost, just in time for the caucuses in Iowa on January 3 and the early primaries which follow in short order. Ms. Winfrey has taken a close personal interest in “The Great Debaters.” Whereas she usually stays at one remove from Harpo’s output, as executive producer, for this movie she is the producer, a much more intimate and involved position which has given her close control over casting, screenplay, and final cut.

The star and director is another African-American supporter of the Obama presidential campaign, Denzel Washington, as are three other members of the cast. They told USA Today at the Hollywood premiere that they were all rooting for Mr. Obama. And the film is distributed by the Weinstein Company, headed by the pugnacious Democratic supporter Harvey Weinstein.

The hero of the movie, the poet Melvin Beaunorus Tolson, played by Mr. Washington, is a true life character who in 1935 coached the debating team at Wiley University, a racially segregated all African-American school in Marshall, Texas, and hauled it to national prominence by trouncing the University of Southern California in the national student debate championships. (For heightened dramatic effect, the movie relocates the final debate to Harvard.) It is a work of considerable power and persuasion, combining the horror of “Mississippi Burning” with the charm of “Little Miss Sunshine,” and concludes with a stirring Hollywood finale in which everything turns out right that would do credit to that master of optimistic all-American outcomes Frank Capra. Its historic message is undeniably intended for the present day.

In one of the early emotionally charged debates against their first white rivals, at Oklahoma City University, the sole woman member of the Wiley team, played by Jurnee Smollett, complains that blacks are continually told to postpone their demands for equal rights with whites. She ends her tearful peroration with the line, “The time is now!” the exact same words Ms. Winfrey employs in her emotive pleas to Democrats and independents to back Mr. Obama. In hammering home the film’s moral, other elements on the screen seem more than mere coincidence. One of the villains is a callow racialist sheriff, whose rural Texan accent and smudgy use of English sound uncannily like George W. Bush’s aberrant twang. The uniformed bands who brutally impose what passed for racial justice in Depression era Texas are, of course, the Texan Rangers, whose name inspired that of the baseball team the president once owned.

The most important and striking parallel, however, is between the quietly spoken and undeniably glamorous figure of Mr. Tolson and the quietly spoken and undeniably glamorous figure of Mr. Obama. Both avoid hysterical invective and softly urge their followers in measured prose to press for peaceful change through existing institutions. Their message is that moderation and the rule of law will eventually ensure that merit rather than ethnicity rules the lives of those born in America without white skin.

The movie’s advertising tag line is, “When the nation was in need, he inspired them to give us hope,” a slogan which makes rather more sense in the context of Mr. Obama’s life than in that of Mr. Tolson.

As far as Mr. Obama is concerned, there is nothing to be lost and a great deal to be gained by such warm encouragement from Ms. Winfrey and her friends in the movie business. The 13 million older housebound mainly white women viewers who make up Ms. Winfrey’s television audience will no doubt spend time considering Mr. Obama’s merits, as they did in September when she recommended them to read Al Gore’s book “An Inconvenient Truth.” But will Mr. Obama’s Oprah moment signify an electoral breakthrough for African Americans? Will white voters see beyond the color of his skin and look upon him afresh because he has received so much attention from his African-American Hollywood friends? It is by no means easy to assess. Had Jay Leno, say, or Barbara Walters lent their names to his campaign, it might have suggested more clearly that the old certainties no longer apply.

If Ms. Winfrey’s dramatic intervention leads to African American voters actually going to the polls, it may win him the Democratic nomination. But would that lead to him winning at the general election?

Opinion polling is of little help in answering that question. While voters are still prepared to be politically incorrect when it comes to answering questions about electing a woman, or a Catholic, or a Mormon, or a Jew, they are not as willing to confess that they hold racist sentiments even to an anonymous telephone pollster. In America, a black candidate remains a bugaboo even when the candidate is as charming and as intelligent as Mr. Obama.

How audiences greet “The Great Debaters” is not much of a guide either. It pleads for tolerance and fairness, but is nonetheless an exercise in special pleading on behalf of African Americans. It will reinforce those who are already tolerant and color blind. Those who are neither will not choose to see it.

Ms. Winfrey once said, “The expectation of my life was that I might be able to work for some good white folks. Now I got some good white folks working for me.” Mr. Obama may already be able to say, “The expectation of my life was that I might be able to vote for some good white folks. Now I got some good white folks voting for me.”

Whether enough of them can make him the Democratic nominee, then propel him into the White House, is one of the key questions which characterize this increasingly fascinating and close fought election.

nwapshott@nysun.com