FACTBOX: Obama condemns ex-pastor's "appalling" remarks

(Reuters) - U.S. presidential candidate Barack Obama, trying to quell a firestorm over racially charged remarks from his former pastor, has condemned the minister's comments as "outrageous" and "appalling."

Obama, who would be the first black U.S. president, used his strongest language yet on Tuesday to distance himself from Rev. Jeremiah Wright, who has blamed the U.S. government for the spread of the AIDS virus and declared "God damn America" as he railed against the country's history of racism.

Wright's comments have been a stumbling block for Obama. The Illinois senator is vying for the Democratic nomination against Sen. Hillary Clinton, who would be the first woman to win the White House. The Democratic nominee will face Republican Sen. John McCain in the November election.

Here is some background on the controversy and its impact.

HOW DID WRIGHT BECOME AN ISSUE IN THE CAMPAIGN?

In mid-March, just as Obama was racking up a series of victories against Clinton and gained the status of the front-runner in the Democratic race, video clips of Wright's sermons began airing on television.

In one sermon, the minister used the phrase, "God damn America," anathema to many in an intensely patriotic nation. He also said he believed the September 11 attacks were retribution for U.S. foreign policy.

Wright recently retired as pastor of the Trinity United Church of Christ in Chicago, which Obama has attended since 1992. Wright presided over Obama's marriage and baptized his two daughters.

Obama gave a widely praised speech on March 18 calling for racial healing and offering a nuanced view of Wright, denouncing the pastor's remarks but declining to disown him.

After keeping silent for weeks, Wright has made a number of public appearances in recent days, including one in Washington on Monday, in which he stood by his inflammatory remarks.

WHAT KIND OF POLITICAL FALLOUT HAS HIS COMMENTS CAUSED?

The Wright controversy has posed problems for one of the central messages of Obama's campaign -- his promise to transcend past divisions such as those involving race.

Obama, son of a white woman from Kansas and a black man from Kenya, has attracted strong support in some heavily white states such as Wyoming, Iowa and Wisconsin.

He also draws strong support from black Americans. Though he remains ahead of Clinton in the number of delegates who will determine the Democratic nominee, he lost to her in two large states, Ohio and Pennsylvania, in part because of his difficulty wooing working-class white voters.

Anecdotal evidence suggests the Wright flap may be contributing to some of his difficulties in attracting these voters.

WHAT IS OBAMA SAYING NOW?