Sen. John Kerry (D-Mass.) is using a database of contact information for about 3 million voters that he compiled during his presidential campaign to position himself for another White House run in 2008. Democratic insiders say that Kerry’s unprecedented direct access to so many current and onetime supporters is a huge advantage heading into the next Democratic presidential primary. But his greatest strength, the experience of winning his party’s nomination last year, is also his greatest weakness, as many former supporters became disillusioned by his loss to President Bush and now blame him for losing a race they believe should...