In early December, amid stagnant poll numbers, Mitt Romney began facing the serious prospect that an underground whisper campaign, spreading rumors about his Mormon faith, would sink his bid for the White House. To counter misperceptions and change the discussion, Romney offered a speech, at the George H.W. Bush presidential library, on the place of religion in the public square.

Many thought the idea of a major address, coming just a month before the Iowa caucuses, was a fatal mistake. But in the aftermath, Romney's poll numbers went up, and his campaign ended up doing well enough to earn more delegates than any candidate but John McCain. By successfully navigating the dangerous waters of a speech on religion, Romney not only kept his candidacy afloat, but finished in better position in several states than pre-speech polling suggested.

Today, Barack Obama faces the same challenge on a similarly taboo yet crucial factor in this year's presidential contest, when he will discuss race in what his campaign is billing as a major address at Philadelphia's National Constitution Center. Like Romney, Obama's speech is a dangerous one to give; but like Romney, Obama can use the address to bolster his campaign.

Race and religion are two topics that neither candidate wants as part of an election debate. For Obama, bringing up race can hurt the image he's spent his political lifetime crafting. Race brings up hundreds of years of negative history and the notion that the conflict is still about one group fighting another. Obama's appeal is the opposite, as a post-racial, post-partisan politician, and about moving past those divisions. Any time people are reminded of the past, they're not looking toward Obama's future.

On the other hand, Hillary Clinton, John McCain and the Republican National Committee won't touch the issue of race either, for fear of instant branding as racists. There are plenty of obvious differences between Obama and McCain, should they face off in November, most notably age, experience and their thoughts on the war in Iraq. Clinton faces her own danger, risking the destruction of the modern Democratic coalition by alienating a hugely important part of the base. Opponents who talk about race against Obama will only speed their own destruction.

The electorate won't say it, but both topics weigh on at least some voters' minds. That division was most obvious in Mississippi, where white voters showed more obvious reluctance to vote for the African American candidate than they had in other states. Too, Obama's poll numbers in several primary states have dramatically over-stated his actual support, suggesting at least some role for the Bradley effect.

Like Romney, who attended the funeral of Mormon President Gordon B. Hinckley in the days leading up to February 5, Obama has a religion problem too. Rumors that Obama is Muslim were somewhat disproven last week with the release of several videos of his former pastor, the Rev. Jeremiah Wright. But Wright's inflammatory statements just substituted one crushing Obama burden for another.

Today's speech will reportedly address Wright's comments as well as the role of race in the campaign. Despite the obstacles, Obama can turn that into a positive, primarily by focusing on a larger picture of the future. In Barack Obama's America, every race can be lifted up, and every race can benefit, he should say.

The difference between Obama and other, older African American leaders is generational. Obama, along with other, new African American leaders like Newark Mayor Cory Booker, Massachusetts Governor Deval Patrick and Washington Mayor Adrian Fenty, did not live through the tumultuous 1960s, when civil rights leaders marched through the streets and clashed with racist authorities in the Deep South.

Instead, they grew up as the first generation of African Americans became millionaires, after segregation and during a period when, compared with the rest of American history, race relations had never been better.

That doesn't mean there isn't anger in the African American community. But casting the discussion about race as about moving the country forward, instead of as a conflict between two inherently adversarial sides, is the key for Obama's speech.

Obama's "hope" slogan, dotting yard signs across the country, is speaking to people. Anything other than the same on race relations and Obama could wind up stumbling over what could become a make-or-break moment in his bid to change history.