It is human nature for people to associate with and support others like themselves -- based on race, ethnicity, religion, gender and other factors. In this segment of How America Elects, VOA's Jeffrey Young examines the impact of so-called identity politics.

Presidential contender Barack Obama went into the South Carolina Democratic Party primary in January with opinion surveys showing him to be the choice of about 60 percent of that state's African-American Democrats. But exit polls that day showed that Senator Obama finished with more than 80 percent of their votes.  Political analysts say that surge was the result of something they call identity politics.

That human tendency to identify with people who share our characteristics has a direct effect at the ballot box, says Georgetown University government professor Mark Rom. "'Identity politics' is when someone casts a vote for a person because of their race, their gender or their ethnicity -- something they can identify with in themselves, and want to see in a candidate," he said.

Analysts say that identity politics came to the forefront in South Carolina after former President Bill Clinton compared Senator Obama's historic bid for the nomination to another, earlier African-American presidential candidate.

"Jesse Jackson won South Carolina twice in 1984 and 1988, and he ran a good campaign,” Clinton said. “And, Senator Obama has run a good campaign here."

Obama is the first African-American that has demonstrated broad multi-racial appeal. A number of African-American voters felt the remark diminished Obama's candidacy and perhaps was meant to turn non-African-Americans away from him.

"When race is being used in campaigns to mobilize white voters, African-Americans then most identify themselves and their politics, and behave in terms of politics, as African-Americans," says David Bositis, who is an analyst at an African-American centered, independent research group, The Joint Center for Political and Economic Studies.

Identity politics is involved in the campaigns of other presidential candidates, too. Senator Hillary Clinton is the first woman to have a serious chance to gain her party's nomination. And many women Democrats, especially those of her middle-aged generation, have embraced this historic opportunity.

"American women have waited a very long time to have the chance to vote for someone like them for president," Rom said.

The Republican Party's presumptive nominee, Senator John McCain, practices what some observers call a different form of identity politics -- shared strong beliefs.

McCain TV Ad: "Keep that faith. Keep your courage. Stick together."

In this ad, McCain appealed to voters who see national pride, security and military strength as paramount.

"Politics is the art of making what appears to be impossible, possible," Hilary Clinton said.

Critics of identity politics say it is oftentimes divisive. But if candidates and their parties can gain advantage by using it, they will.