Here we go -- the Ambinder Shortlists, based mostly on educated guesswork and as many conversations as one reporter can reasonably have. I have excluded from these lists candidates I consider -- based on reporting -- to be implausible. These lists will change as the information changes.

Sen. John McCain.

1. Gov. Tim Pawlenty (R-MN) -- He's the favorite.

The rest, in no particular order:

#. Gov. Mitt Romney (R-MA) -- working hard to earn respect of McCain
#. Gov. John Hunstman, Jr. (R-UT) -- nice man; solid tenure as government official
#. Sen. John Thune (R-SD) -- underwhelms as a surrogate but McCain bonded with him over family history
#. Gov. Mark Sanford (R-SC) -- McCain respects his decision not to endorse in the primary

Sen, Barack Obama

1. vacant. Just to be provocative, I'll throw out Joe Biden's name. His hidden asset is his connection with white, working class voters. His obvious asset is his foreign policy experience and.

The rest:

#. Ex-Sen. Tom Daschle (D-SD) -- he has powerful allies in Obama's inner circle; Midwestern credentials; government know-how; credibility with white working class voters;
#. Gov. Janet Napolitano (D-AZ) -- Obama really likes her.
#. Sen. Chris Dodd (D-CT) -- his donors will pressure Obama; Dodd and Obama have become close friends
# Sen. Jim Webb (D-VA) -- the narrative would be awesome
# Chuck Hagel (R-NE) -- Hagel himself seems to want Obama to ask him to join the ticket.

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