Will It Be an Obama-Bayh Ticket?

Top Democratic Party officials are expecting Sen. Barack Obama to select Indiana Sen. Evan Bayh as his running mate as early as midweek. "He brings state and federal experience, helps us in the Midwest, and is a good complement to Barack," said a top party source.

However, the source noted, Obama hasn't signaled yet who his pick will be, and a number of other candidates, including New Mexico Gov. Bill Richardson and Virginia Gov. Tim Kaine, are still under consideration.

Party officials are expecting the announcement earlier rather than later this week so that the Democratic ticket can capture the media coverage leading into next week's Democratic National Convention in Denver. "They'll want to show the new ticket off and give it a good walk-up to Denver," said the official.

The campaign has been ready for over a week to have the running mate on board, having hired a full staff to handle the new candidate.

On the Republican side, Sen. John McCain is still hiring his vice presidential nominee's staff, having just selected a spokeswoman, Maria Comella, the former spokeswoman for Rudy Giuliani. She worked for the Bush-Cheney 2004 re-election as part of Steve Schmidt's press show. He now runs McCain's campaign.

There is more uncertainty about who McCain will pick for a running mate, though Republican officials said that earlier expectations that he would spring a surprise pick are being muted by concerns that a newcomer to the political scene, such as former eBay boss Meg Whitman, would be too politically green to run on the national stage.