WASHINGTON — Senator Obama has a habit of telling interest groups what they don’t want to hear, even at the risk of alienating audiences critical to the prospects of a presidential candidate.

Not to be undone by his rivals, the Illinois Democrat has made remarks befitting the myriad of forums and debates he’s attended, praising the work of unions, upholding Israel to Jewish groups, and decrying President Bush’s spending on education.

But he’s also uttered words not often heard, especially when Democratic constituencies gather. For example:

• Mr. Obama told the National Education Association that performance-based merit pay ought to be considered in public schools.

• Cuban exiles are considered one of the keys to winning Florida, but he disagreed with leaders who want a full embargo against Fidel Castro’s government and instead called for allowing travel and money to the island.

• Michigan voters play an important role in national politics, but Mr. Obama visited Detroit to lecture the state’s biggest industry for failing to improve automobile fuel efficiency.

“I don’t do this for shock value,” Mr. Obama said in a recent interview while campaigning in New Hampshire.

“There may be people who chose not to support me because I’m not telling them what they want to hear or reinforcing their preconceptions,” he told the Associated Press. “I want to be elected to the presidency not by having pretended I was one thing and then surprise people with an agenda, but to get the agenda elected, to get a mandate for change. And you can’t do that if you’re not doing some truth telling.”

Mr. Obama’s approach was a signature of President Clinton, his chief rival’s husband, in the 1992 presidential campaign. The strategy is known in modern politics as a “Sister Souljah.”

In addressing a black audience, Mr. Clinton accused the hip hop artist of inciting violence against whites. Some black leaders criticized Mr. Clinton, but it helped reinforce his image as a voice of moderation against crime who refused to pander.

Also in 1992, Mr. Clinton gave back-to-back speeches to a black audience in Detroit and a white audience in the city’s suburbs, challenging both to reach across the racial divide to bring political change. A year into his presidency, Mr. Clinton told black ministers in Memphis that they must do more to stop violent crime in black communities.

“Telling a friendly audience something they don’t want to hear is a signal that you can stand up on the tough issues,” Democratic consultant Jamal Simmons said. “There will be people who will be upset, but many times the audiences aren’t the people in the room but the people on televisions who see you telling you something to a friend that they don’t like.”

Mr. Simmons said the politician also has to have enough credibility with the audience to deliver a tough message like telling blacks they need to do more to stop crime. “Other than Bill Clinton, I don’t know a white politician who could say it,” he said.

Since Mr. Obama offers blacks a chance to put one of their own in the White House for the first time, he comes with instant credibility. He has told blacks that they are letting homophobia stop them from fighting the spread of sexually transmitted diseases. He repeated a similar message at the largely white Saddleback megachurch, telling the congregation that they should stop preaching abstinence only and instead promote condom use.

He says blacks need to vote and clean up their neighborhoods. He has decried movements against affirmative action and unequal spending in black and white schools, but he has said parents also have a responsibility to better educate their children.

“Turn off the television set and put away the Game Boy and make sure that you’re talking to your teacher and that we get over the anti-intellectualism that exists in some of our communities where if you conjugate your verbs and if you read a book that somehow means you are acting white,” he said during a speech in Selma, Ala., to commemorate the civil rights march there.