Artur Davis, a former Democratic congressman from Alabama, has been a Republican for only a few months. But his speech tonight at the Republican convention is important because he reflects a major theme of Mitt Romney’s campaign against President Obama and another theme promoted by the GOP.

The Romney theme is that it’s okay to have changed your mind about Obama. Davis, an African American and a political moderate, seconded the nomination of Obama at the Democratic convention in Denver in 2008. But he’s been disappointed in the Obama presidency and today supports Romney.

“I’m one of millions of people who, frankly, didn’t get what we voted for,” he told Fox News in May, just after switching parties. “A lot of people in my old state of Alabama—15 Democratic elected officials—have now become Republicans. The guy who defeated me in the Democratic primary [for governor in 2010] now works for the Republican governor who defeated him. A lot of us have made this move in some way, shape, or form.”

Davis deals with a specific worry of Republican strategists: that since millions of swing voters who backed Obama in 2008 still like him personally, they’ll be reluctant to desert him in 2012.

Republicans have unleashed a major effort to turn these disillusioned voters into Romney supporters. The Romney campaign aired a soft-hitting TV ad featuring Obama voters four years ago who have jumped to Romney. Americans for Prosperity, a conservative group, has run two ads on this point. And a 60-minute film, produced by Citizens United and released today, consists of liberal independents and registered Democrats who explain why they’ve given up on Obama.

A Harvard Law School graduate, Davis, 44, is the most prominent switcher. He was elected to the House as a Democrat in 2002 and served four terms. He was the only member of the Congressional Black Caucus to vote against Obamacare.

He also meets a special need of Republicans: attracting African-American voters and candidates. This has been on the wish list of Republican officials for decades, though not always a high priority. The GOP’s inability to win over African Americans was acute in 2008, when Obama won 95 percent of the African-American vote.

But two years later, two black Republicans, Allen West in Florida and Tim Scott in South Carolina, were elected to the House from largely white districts. In 2012, Republican Mia Love, an African American and a Mormon, is regarded as a strong candidate to win a House seat in Utah.

Davis represents a different facet of the GOP push—that is, to persuade moderate-to-conservative African-American Democrats to change parties. Davis has explained his switch as a reaction to Obama’s liberal policies. “I may be a minority in this regard, but I’m one of the people who supported Barack Obama because I thought that he was in the center,” he told Fox.

“I thought he was going to be a pro-growth president. I thought that his focus at all times was going to be national unity and bringing the country together, and I saw an enormous amount of potential,” Davis said. “What did we see? We saw a very different path.”

Davis, who now lives in Virginia and may run for office there, said he’s “on the center-right. There is no center-right in the Democratic party. There is in the Republican party, and I want to help it and be a part of it.”

Scott—he represents Charleston, South Carolina, where the Civil War began—said Davis is “symbolic” of a shift “that is happening in the minority community. It’s a gradual process, but a real process.”

“There seems to be a movement on the local and state level,” Scott said, of black Democrats who want “to align with their values” rather than with their history as Democrats. “We’ll continue to see that shift.” ♦