Rob Portman for the GOP veep? Not if 2008 is any guide

Sen. Rob Portman (R) of Ohio is the insider favorite to ride shotgun on Mitt Romney's presidential campaign. Taking a look back at the 2008 veepstakes, however, helps demonstrate that the conventional wisdom on vice-presidential picks is almost always wrong.

First, let's establish how much of a front-runner Senator Portman is at this point. Two-thirds of state Republican Party chairs and members of the Republican National Committee polled by online news site BuzzFeed said Portman was both the best and most likely pick. Several notable political columnists have singled out Portman. A National Journal poll from earlier this month showed Portman the choice of 15 percent of Republican insiders versus Florida Sen. Marco Rubio (R) at 22 percent, while online prediction market Intrade shows the two senators knotted with 15 percent probability of getting the nomination.

Of course, there's a wide difference between 66 percent and 15 percent. The former is as close as you can get to a political slam dunk. The latter is more like a contested three-pointer.

Past behavior is no guarantee of future performance, to be sure. But do you know who the front-runners were for John McCain and Barack Obama in 2008 at this point?

For Mr. Obama, then-Gov. Kathleen Sebelius of Kansas was in the driver's seat. For Senator McCain, it was then-Gov. Tim Pawlenty of Minnesota. According to The Fix, The Washington Post politics blog run by Chris Cillizza that's as good an aggregator of inside D.C. opinion as any, the rest of the Top 5 veep candidates were as follows:

Obama

5. Sam Nunn, former Georgia senator

4. Tim Kaine, then governor of Virginia

3. Hillary Rodham Clinton

2. Ted Strickland, then governor of Ohio

McCain

5. Mitt Romney

4. Charlie Crist, then governor of Florida

3. Rob Portman

2. John Thune, South Dakota senator

As you can see, not only did the front-runner from early in the 2008 process not make it, but the eventual picks weren't even in the Top 5.

Why is this? Presidential campaigns dig deep into the backgrounds of each prospective vice president, weighing his or her political résumé, personal story, and electoral prospects or drawbacks. (This third concept, however, hasn't been a strong determinant of VP picks over the past half century.)

Also, the prospective president has to be able to actually work with his or her vice president. Then there's the dark but serious prospect that Bill Clinton raised with adviser Paul Begala before Mr. Clinton selected Al Gore. "Why pick him?" Mr. Begala asked. "Because Paulie," Clinton said, "I might die."

This test, Begala says, all but guarantees Portman's selection to the second line on the Romney ticket. But whether a presidential candidate feels that the VP pick would pass this ultimate test isn't something we're likely to see hashed out in the public space.

As the candidates take their turns at Mr. Romney's side, he will probably develop a deeper sense of what makes these candidates tick well away from the eyes of insiders of all kinds. For example, Portman has worked next to Romney in Ohio, while Rep. Paul Ryan (R) of Wisconsin stumped with Romney before the Wisconsin primary.

Still not convinced of the mercurial and unpredictable nature of the veepstakes? Consider how quickly Senator Rubio's fortunes have changed. Although he's stumping with Romney in Pennsylvania on Monday in what some consider to be a vice-presidential tryout, Florida's junior senator was the pick to click by 60 percent of Republican insiders last October.