Artur Davis' decision to speak at the Republican National Convention dovetails well with the GOP's attempt to capitalize on disappointment with President Obama. Davis, who represented Alabama's 7th Congressional District from 2007 to 2011, was one of Obama's earliest supporters and the first politician outside of Illinois to endorse the then-senator's presidential bid.

In 2009, seeking to replicate Obama's success on a smaller scale, Davis announced his candidacy for governor of Alabama. Had he won, Davis would have been the first African American to win a gubernatorial seat in the Deep South as well as Alabama's first African-American governor. But to win, Davis needed to broaden his appeal beyond the state's predominantly black Democratic Party and attract support from Alabama's white, conservative majority.

In practice, this meant opposing the priorities of the now-President Barack Obama. Davis supported the stimulus but was a vocal critic of the health-care bill and eventually voted against it. He did as much as possible to distance himself from Alabama's Democratic establishment. In his race for the party's gubernatorial nomination, he avoided prominent African-American groups and tried as much as possible to convince whites on both sides of the aisle that he could be their first black governor.

The result of this maneuvering was a landslide loss. His opponent, Ron Sparks, a white Democrat, took 62 percent of the vote to Davis' 38 percent.

Davis had so alienated African Americans with his opposition to health-care reform that, when it came time to vote, he lost the black vote - in a Democratic primary - by huge margins.

Like Connecticut's Joe Lieberman before him (and Zell Miller before that), Davis can tell a credible story of ideological alienation. He thought that the Democratic Party was a big tent but now - under Barack Obama - it is a haven for intolerant leftism. This isn't the most accurate description of what happened; voters rejected Davis for standing against their interests, not because he was too conservative, but it's compelling as far as these things go.

Obviously, Davis' remarks in Tampa won't persuade black voters to oppose the president. But this speech isn't meant for them. To highlight the defection of a prominent African-American supporter of Obama is to send a subtle message to indecisive whites - it's okay if you're disappointed with Obama, you can vote against him with a clean and unprejudiced conscience.

Jamelle Bouie is a staff writer at the American Prospect, a magazine covering politics, policy and culture from a liberal perspective. She wrote this piece for The Washington Post.