By Lowman S. Henry

Now that Barack Obama appears to have derailed the Clinton regime's return trip to the White House, speculation is beginning to pick up on who might be the Illinois senator's running mate.

Both Pennsylvania Gov. Ed Rendell and our state's Democratic U.S. Sen. Robert P. Casey Jr. are being prominently mentioned. The Keystone State has not had a resident in either the White House or in the vice president's office since James Buchanan, and chances are that the drought will not end this year.

It is true that selecting either Rendell or Casey would likely lock up Pennsylvania and its treasure trove of 21 electoral votes for Obama. It is axiomatic that a nominee must win two of three swing states - Pennsylvania, Ohio or Florida - in order to claim the presidency. George W. Bush did in it 2000 (yes, he really did win) and 2004 by posting victories in Florida and Ohio, but he lost Pennsylvania both times.

Ohio has been trending heavily Democratic in recent years, but Florida remains a toss-up, so winning Pennsylvania would be vital to Obama's chances. Right now polls suggest that Penn's Woods is up for grabs. Therefore, a move that would cement his standing here would be politically prudent if not decisive.

There are problems with either choice. Casey's convincing win over incumbent Republican U.S. Sen. Rick Santorum in 2006 proved that the Casey name is still magic in Pennsylvania. But part of that magic is that Casey is pro-gun and pro-life (although not as dedicated to the position as was his father). It was not all that long ago that the party hierarchy banned Casey Sr. from addressing the Democratic National Convention because of his pro-life stand, so his son's selection would amount to a major turnaround.

It is inconceivable that the Democratic Party's base would accept a pro-life vice presidential nominee. Former Pennsylvania Gov. Tom Ridge, who could do for John McCain what Bob Casey would do for Obama, has the same problem on the Republican side. The GOP base simply won't accept a pro-abortion nominee on the national ticket. Thus, both Ridge and Casey are disqualified.

As for Rendell, he proved his political prowess by decisively delivering Pennsylvania for Hillary Rodham Clinton in the April 22 primary. That is his strength and his weakness. He is not by any means an Obama insider, which is a negative. But his selection would go a long way toward uniting the party and bringing Clinton's supporters - who will be disheartened after losing a close, hard-fought race - back into the fold.

Rendell himself dismissed the possibility of being on the national ticket, saying he is not second-banana material. He knows himself well. After two terms as mayor of Pennsylvania's largest city and a term and a half as governor, Rendell is used to being the chief executive and calling the shots. Unless he were given Cheney-like responsibilities in an Obama administration, the role would not suit him well.

Perhaps the biggest drawback when it comes to Rendell is who would replace him as governor of Pennsylvania. Lt. Gov. Catherine Baker Knoll is the Democratic Party's version of the crazy aunt in the attic. She is a grandmotherly figure who is well liked, but who also completely lacks the ability to function as governor of one of the nation's largest states.

With Flavia Colgan, her erstwhile top staffer, out trying to become a CBS News maven, Knoll even lacks the staff infrastructure to handle the duties of governor. The lieutenant governor only makes the news for her frequent malapropisms, most recently for a tongue-lashing she gave Pittsburgh Mayor Luke Ravenstahl and Allegheny County Executive Dan Onorato over what she perceived as insufficient recognition at a political event. Simply put, neither Rendell nor Pennsylvania could withstand two years of Knoll in the governor's mansion.

That having been said, this is a wild and crazy political year and anything can happen. Six months ago conventional wisdom held that Rudy Giuliani and Hillary Clinton would wrap up their respective party nominations early and embark on one of the longest general election campaigns in history. Neither will be standing at the lectern this summer accepting a nomination.

So, it is unlikely that either Casey or Rendell will grace a national party ticket this year - but don't bet your sub-prime mortgage on it.

Lowman S. Henry (lhenry@lincolninstitute. org) is chairman and chief executive officer of the Lincoln Institute and host of the weekly "Lincoln Radio Journal."