I just got off the phone with top Joe Lieberman adviser Dan Gerstein, and he acknowledged to me that the Lieberman camp doesn't have any direct evidence that the Lamont campaign -- or Lamont supporters -- are behind the alleged hack attack on the Lieberman campaign web site.

Gerstein reiterated the belief that Lamont "supporters" were behind the attacks, and said he wanted Lamont to condemn the tactic, but said: "We are not putting the blame on the Lamont campaign."

Asked if the Lieberman campaign knew who was behind the alleged attacks, Gerstein said: "We don't."

Lieberman campaign manager Sean Smith has directly accused Lamont supporters of being behind it, adding: "If Ned Lamont has a backbone in his body, he will call on these people to cease and desist." And Gerstein earlier today said of Lamont, "Their supporters are doing these [attacks], we've demanded they get them to stop and they refuse to do it."

But when I asked Gerstein if the Lieberman campaign any had evidence that Lamont backers were behind the attack, he didn't answer directly. He said: "Here’s the thing. We are not putting the blame on the Lamont campaign...We think it's very important for them to put out a statement throughout the Net roots that they not only don't support these tactics, but want them to stop."

I noted that the Lamont campaign Web coordinator, Tim Tagaris, had posted a statement disavowing any campaign involvement and calling on anyone doing the attacks to stop. But Gerstein said that still wasn't enough. "We asking it to come directly from Ned Lamont and that they aggressively circulate that statement."

The argument the Lieberman campaign appears to be making, then, is that though they don't have any evidence that Lamont supporters are behind the attack, the candidate himself should demand a cessation of the attack from any supporters who might have done it.