The political bottom line of last night's primary election debate between incumbent Sen. Joe Lieberman and challenger Ned Lamont (video clips available at PoliticsTV) is that Lamont is still standing and taken seriously.

For an outsider candidate, you can't ask for much more than that.

The name of the game is to cross the threshold of plausibility, at least in the minds of the media, so you get the necessary coverage and the opportunity to make a case to the voters all the way through Election Day.

To deny that from happening, Lieberman took a calculated risk:

Sacrifice his nice, civil high-minded persona and the gravitas that comes with being a 3-term Senator, in order to relentlessly attack Lamont and hope the rookie cracks on live TV.

In the 2000 VP debate, Lieberman opened by saying, "I am going to be positive tonight. I'm not going to indulge in negative personal attacks" and later added "I have great respect for Dick Cheney ... and I don't have anything negative to say about him."

Whereas last night, he was trying to hammer Lamont from the very begininng, claiming Lamont has taken multiple positions on Iraq, and ominously asking the question "Who is Ned Lamont?" -- the classic move to raise doubts about a political newcomer.

Yet the rookie kept his composure.

So instead of a quick knockout punch and a cruise to victory, Lieberman is now more likely to face a tough slog.

But the debate also leaves Lamont with plenty of his own slogging to do.

While he scored some points as he began to broaden his argument beyond Iraq, he also had no knockout punch that will instantly convince those Dems not yet on the Lamont train that Lieberman harms Democratic goals enough to warrant dismissal and, theoretically, risk a safe seat.

Though the debate did provide some openings for Lamont.

In particular, Lieberman's defense of his vote for Bush's fossil fuel-laden energy bill was convoluted and showed weakness.

This is not only an subject that is very much on people's minds, it also is an issue that reinforces the hollowness of Lieberman:

He talks a good game on the environment and boasts endorsements from reputable groups, but when you need his vote and his leadership, it's not there.

So Lamont would be well-served to increase his emphasis on energy.

Also, Lamont should play up Lieberman's attempt to misrepresent his own position on Iraq.

Lieberman stressed in the debate, "I'm not for an open-ended committment to Iraq."

Yet as LiberalOasis has noted repeatedly, Lieberman has been enthusiasatic about permanent military bases in Iraq -- a never-ending committment -- from the very beginning of the war.

And last November, he voted against a Dem Senate amendment that said troops should not stay indefinitely.

In the debate, Lieberman tried to raise the canard that it is Lamont who wouldn't level with Connecticut voters about his position on Iraq.

But it is Lieberman who does not have the guts to look voters in the eye, during a hotly contested election, and say he supports permanent military bases.

In the debate, Lamont rejected permanent bases in Iraq, but did not explicitly point out that Lieberman is on the record supporting them. He should.