Via Jason, I see Mike Allen is reporting that Mitt Romney is now McCain's top veep prospect. The rationale, Allen says, is money:

One of the chief reasons the Massachusetts governor is looking so attractive is his ability to raise huge amounts of money quickly through his former business partners and from fellow members of The Church of Jesus Christ of Latter-day Saints, the Mormons.

McCain sources tell Politico that they believe Romney could raise $50 million in 60 days. One close Romney adviser said it could even be $60 million.

One thing I'm genuinely unclear on: If, as expected, McCain stays within the public financing system for the general election, how useful is the money Romney raises? Allen says Team McCain is likely to announce its veep choice shortly after Obama announces his, presumably in early August. Under the public financing rules, that would leave the McCain-Romney ticket about a month to spend any money it raises, which means Romney's ability to raise $50-$60 million in 60 days wouldn't necessarily be that helpful. Is it possible that McCain would follow Obama in opting out if Romney joins the ticket? (That would also free Romney to spend his personal wealth, no?*) Or would the money raised after the GOP convention just go to the RNC? Or would Romney start raising the money even before he was officially announced?

Thoughts welcome...

*The PR damage from opting out to tap Romney's personal wealth would probably be significant (not least because Obama would be able to remind us he opted out to tap millions of small donors)...

--Noam Scheiber