Former Virginia Gov. Tim Kaine has purchased $1 million in new airtime for the fall, bringing his total ad reservations to a full $3.5 million, a source familiar with the buy tells me.

Kaine had previously purchased $2.5 million in TV time -- that means actually laying down the cash now, as opposed to simply reserving the time. The additional seven-figure buy is a measure both of Kaine's financial resources and the competitiveness of the race.

Kaine's Republican opponent, George Allen, reserved just over $3 million in fall airtime at the end of June. So on top of the already heavy presidential campaign advertising, Virginians can look forward to a major firefight in a Senate race that's expected to be one of the country's most expensive.