The Buzz Around Portman, the Un-Palin - He's moderate in style but generally well-liked by his party's conservative wing. Beyond credentials, there is the matter of the political importance of Mr. Portman's home state of Ohio. No Republican has ever won the presidency without carrying it,

Gerald Seib writes in The Wall Street Journal:

As Mitt Romney ponders his choice of a running mate, the case for Ohio's Rob Portman is fairly simple: He wouldn't hurt the Romney cause in any significant ways, and could help it in others.

If that sounds like an underwhelming argument for Sen. Portman, it isn't. In the eyes of some Romney advisers, the one thing the presumptive Republican nominee can't afford to do is replicate his party's 2008 choice of Sarah Palin, who soared on the excitement scale but appeared unprepared for the presidency. She also served as a regular distraction from the actual presidential candidate, Sen. John McCain, and ultimately became a reason to question his judgment.

And if the goal is to avoid a Palin-like experience—well, Rob Portman is the un-Palin of 2012. His résumé is sterling. There is no chance his credentials would be questioned, little chance he would hurt the ticket and only a slim chance he would commit a distracting gaffe.

These aren't small things to a campaign already famous for its methodical approach. Whether they are reason enough for Mr. Romney to pick him is, of course, anybody's guess. But this picture explains why Mr. Portman has, in the past few weeks, gone from oft-mentioned to most-mentioned vice-presidential choice.

The case for Rob Portman starts with that résumé. He served in the House for a dozen years before being elected to the Senate. He was head of White House legislative affairs for President George H.W. Bush, and held two cabinet-level positions—U.S. trade representative and director of the Office of Management and Budget—in the George W. Bush administration. He was part of the congressional supercommittee that tried—and failed—last year to come up with a master deficit-cutting plan.

He has practiced law and has helped run two family businesses in Ohio. He's moderate in style but generally well-liked by his party's conservative wing.

At the same time, he's actually done things with Democrats. When in the House, he often worked with a liberal Democratic colleague from Maryland, Ben Cardin, now also in the Senate. In recent weeks, he quietly helped work around conservative opposition within his own party to extend funding for the Export-Import Bank, a top business priority that had become endangered by ideological wrangling.

Beyond credentials, there is the matter of the political importance of Mr. Portman's home state of Ohio. No Republican has ever won the presidency without carrying it, and there is a high probability it will be essential again to Mr. Romney's chances.

Would he carry his home state for Mr. Romney? There is no guarantee, of course, but he'd likely help. In the course of his seven successful elections to a Cincinnati-area House seat, the share of the vote he won ranged from 70% to 77%.

When he ran for the Senate in 2010, it was assumed his problem was that he wasn't particularly well-known outside that home base of Cincinnati. Yet he raised a ton of money and destroyed an opponent well-known around the state, Lt. Gov. Lee Fisher, winning the race 57% to 39%, and carrying 82 of Ohio's 88 counties. He ran credibly in Democratic areas of the state.

Still, there are two significant arguments against Mr. Portman. The first is that his work as budget director in the latter stages of the George W. Bush administration would make it easier for the Obama campaign to underscore the case that the deficits that now plague Washington actually took root during the Bush years, and that a Romney presidency would simply mark a return to Bush economic policies that precipitated the great economic slide of 2008 and 2009.

The Portman response would be that he pushed back against deficits internally, persuading Mr. Bush to issue his first veto of a spending bill. "I sent to Congress a five-year, not a 10-year, but a five-year-balanced budget," he argued during a recent breakfast sponsored by Bloomberg View. "Wouldn't that be great to do today?"

The second argument against Mr. Portman is that he's simply too much like the Republican candidate himself, and therefore would represent a missed opportunity to broaden the ticket or provide an added attraction. Like Mr. Romney, he went to an Ivy League college (Harvard for Mr. Romney, Dartmouth for Mr. Portman). Both like numbers. Both can seem more comfortable with process than politics.

In other words, a Portman pick would risk the dreaded characterization of a "two boring white guys" ticket.

On the other hand, Mr. Portman may prove more intriguing than he seems at first glance. He speaks fluent Spanish, for example, and is an accomplished hunter and kayaker. Besides, lots of Republicans figure they got enough vice presidential excitement in 2008 to last a lifetime.