Virginia Gov. Timothy M. Kaine has told close associates that he has had “very serious” conversations with Sen. Barack Obama about joining the Democratic presidential ticket and has provided documents to the campaign as it combs through his background, according to several sources close to Kaine.

. . . Aides to Kaine declined to comment about the possibility that Obama might pick him, referring all questions to the senator’s campaign. “The governor has been pretty clear from the beginning, when Senator Obama asked him to be a national co-chair, that any conversation he has with the campaign, on any topic, are conversations that he is keeping private,” said Delacey Skinner, Kaine’s spokeswoman.

But several people who have spoken to Kaine said he has talked about the seriousness of the possibility. Each spoke on the condition of anonymity, citing the campaign’s desire to keep the process secret. One said Kaine has stressed that there are other top candidates but described his discussions with the campaign as “very serious.”

Two other associates said Kaine’s staff is providing the background information necessary to allow the campaign to search for potential political land mines. One source said Kaine chief counsel Larry Roberts is coordinating with Obama’s team.

You have to wonder whether, somewhere, an Obama aide is putting a big black “X” next to Kaine’s name with the note, “Can’t keep his f—ing mouth shut”…