Barack Obama has picked his running mate, said Jake Tapper in ABC News’ Good Morning America blog, but he won’t be telling the rest of us just yet. He won’t reveal what has become the “best-kept secret” of the presidential campaign until the end of the week, ahead of next week’s Democratic convention. But the rumor mill has narrowed the field to three candidates: Delaware Sen. Joe Biden, Indiana Sen. Evan Bayh, and Virginia Gov. Tim Kaine.

You’re forgetting someone, said radio commentator Taylor Marsh in her blog. “Obama needs someone who can do what he can't do: fight like hell.” And that makes Hillary Clinton “the best person for the job.”

Biden’s stock appears to have “risen sharply lately because of world events,” said Dan Balz in The Washington Post. The resignation of Pervez Musharraf as Pakistan’s president and Russia’s war against Georgia underscored the need for Obama to choose a running mate with experience, and a weekend visit with Georgian President Mikheil Saakashvili called attention to Biden’s foreign policy credentials.

The need for someone with foreign-policy stature pretty much excludes anyone who is a governor of a small or medium-sized state, said John Nicholls in The Nation’s Campaign ‘08 blog. So we can cross Kaine and Kansas Gov. Kathleen Sebelius off the list. And the same goes for Bayh, “whose record of accomplishment in the Senate can best be summed up as ‘Democrat from Indiana.’”

Biden has “gravitas," said Mark Silva in the Chicago Tribune’s The Swamp blog, but he also has a certain “ho-hum quality.“ The weeks of speculation about vice-presidential picks have drained Obama’s campaign of excitement, and he needs to use his selection to rekindle the fire. Kaine could help Obama carry the battleground state of Virginia, and he might just “fill the bill of excitement.”