What do the Democratic National Convention, Plamegate, and Bush Political Intelligence Leaks have in common?
This

Simon, start up the Waaaay-back Machine.

Cut to the Democratic National Convention, Boston, Mass. The Administration has an unwelcome suprise for the Kerry campaign. A "special terrorist alert," nationally annouced, which covered only a few buildings in the entire country. To counter charges of playing politics, the Administration included, for the first time, evidence of the source of the intelligence came from. It came from Naeem Noor Khan.

Khan was a first--a live Al Qaeda leader who agreed to work as a double agent.
Khan's computer contained two sets of plans--one for a coordinated attack on the financial buildings Bush's "alert" concerned. The other plans involved a multiple-bomb plot on the London Underground. Pakistani intelligence had opened Pandora's box. They were able to infiltrate an active Al Qaeda operation while it was going on. This was more than stopping a plot, it was the intelligence opportunity of the war--the inner workings of Al Qaeda at our fingertips.
The operation was paying off, too. Mr. Naeem Noor Khan was in communication with an Al Qaeda cell in Luton, England. MI-5 had them in their sights. They were going to reel in the whole lot.
Until Bush's announcement, that is. The Pakistanis were tipped by the announcement--and the British police swept 12 of them up. The Administration publicly apologized to Britain for the incident in September, 2004.
Unbeknownst to the British, 6 other members avoided the dragnet. On Thursday, July 7, 2005, four of them left for London on the train from Luton.