When Republicans announced the lineup of speakers for their national convention earlier today, nearly every oft-mentioned contender for the vice-presidential slot on John McCain's ticket had a prominent speaking role.

One dark horse VP candidate who does not appear on the list of speakers is Rob Portman, the former Ohio congressman, U.S. trade representative and White House budget director.

Portman plans to be at a McCain event in Dayton, Ohio, the day after the Democratic convention. That's the day Politico's Mike Allen reported -- and GOP officials are not batting this down -- that McCain will make his announcement. Portman's camp says don't read anything into Portman's attendance -- it is routine for Portman to appear at McCain's Ohio events.

"Whenever McCain is in Ohio, Rob wants to do whatever he can to help," longtime Portman aide and now private-sector colleague Rob Lehman told me yesterday.

More on this later, but Portman would bring something to the ticket that is rare among modern Republicans: strong relationships with Congressional Black Caucus leaders and more than lip service on honoring African American history.

Portman has always been viewed as a fringe possibility for McCain and has said he isn't being vetted. But, as I pointed out in a previous post, he has gone through the White House vetting process and two Senate confirmations just during the second Bush term.

The stock of consistent abortion foes such as Portman must be rising after social conservatives have balked at the prospect of an abortion-rights supporter like former Pennsylvania Gov. Tom Ridge or Connecticut Sen. Joe Lieberman finding his way onto the ticket.

Portman's resume is his greatest asset and his most significant liability.

Democrats are doing their best to tie McCain to President Bush, and Portman's jobs in the administration -- as well as his close relationship with the Bush family -- could help solidify that link. On the other hand, he would balance McCain's independent streak, provide geographical balance and bolster the GOP ticket on domestic policy.

He was a critical player on the Ways and Means Committee, which writes laws governing taxes, Social Security, Medicare, pensions and trade, was the nation's chief budget bureaucrat and pushed the nation's trade agenda.

He could not be better prepared for the lone vice presidential debate. Portman has played the roles of Al Gore and John Edwards in prepping Bush and Vice President Dick Cheney for debates.

In a race against the first biracial nominee of either major party, McCain's former opposition to the Martin Luther King holiday and some other civil rights matters leave him open to charges of insensitivity to African Americans. He has visited important historical sites in the Civil Rights Movement this year, including Selma, Ala., and the Lorraine Motel in Memphis.

But McCain's vulnerability was exposed when he drew a sharp rejoinder from civil rights icon John Lewis this week after citing Lewis as someone whose counsel he would seek

It is almost unimaginable that Portman, who has strong credentials on matters of civil rights and a history of working with African American leaders, would get a similar response. Here's how Lewis described him to me in December 2006 for a story in CQ Weekly:

"All of us had a tremendous amount of respect for him," said Lewis, a senior member of the [Ways and Means] committee. "I don't think he ever looked down on us as Democrats with disdain. He treated us as equals, and I can't say that about all members of the other party."

Portman worked with longtime Cleveland congressman Louis Stokes on legislation aimed at preserving Underground Railroad sites through the National Park Service -- and he worked to  secure funding for the Underground Railroad Freedom Center in Cincinnati.

Former Congressional Black Caucus Chairman Elijah Cummings, D-Md., has been even more effusive than Lewis in praising Portman:

"Portman's a very special man ... He's just a decent human being, and I don't think you get so caught up in the party label with him because you feel he is pretty much coming from his heart."

You can read my entire 2006 CQ Weekly story on Portman's early efforts to reach across the aisle after the jump.