Multiple outlets are reporting that John McCain has arrived at a final decision about the identity of his running mate, and that the person chosen will be notified at some point today. An official announcement will likely come on Friday.

As I mentioned earlier this week, some McCain aides were reportedly discussing the possibility of making the announcement tonight, the same night as Barack Obama's speech to the Democratic convention. It seems like that plan is dead, but that doesn't mean McCain's pick might not step on Obama's speech anyway. As you'll recall from this past weekend and the announcement of Joe Biden as Obama's running mate, once the logistics of the rollout get set in motion, there's more of a chance of leaks and other sorts of clues.

At the moment, prominently included among the names being floated as possible picks are former Massachusetts Gov. Mitt Romney, Minnesota Gov. Tim Pawlenty and Connecticut Sen. Joe Lieberman.

Lieberman may be the riskiest pick of the three because of the potential that choosing him would alienate social conservatives, so it's not too surprising to hear the reports that Karl Rove was working behind the scenes to shut down a McCain-Lieberman ticket. Politico's Jonathan Martin reports that Rove called Lieberman last week to ask him to tell McCain he's not interested in the job. That sounds remarkably like part of columnist Robert Novak's recent report about Lieberman, and obviously Rove and Novak have a long reporter-source relationship.

Update: McCain himself, in a radio interview this morning, said, "I haven't decided yet."