I was doing a radio interview this morning on the Connecticut Democratic primary for the U.S. Senate — roughly the 50th in recent days — with Jay Marvin, whose show on KKZN-AM in the Boulder-Denver market is one of the smartest progressive talk radio programs in the country.

Jay doesn’t pull punches. He asked straight up: “Is Ned Lamont going to beat Joe Lieberman?”

I thought for a second and answered: “Yes, I think Lamont’s going to pull this thing off.”

It was the first time I had dared suggest, on tape and without the usual qualifications, that a pro-war Democratic U.S. senator could lose his own party’s primary to a candidate running on a progressive anti-war platform. To be honest, I am still a little uncomfortable making predictions about this race, as the politics of Connecticut Democratic primaries are complex and prone to unexpected shifts.

But the latest survey from Connecticut suggests that Lamont may well be pulling away in this contest. A new Quinnipiac University Poll of 890 Democrats taken July 25-31 has Lamont at 54 percent to 41 percent for Lieberman, the three-term incumbent whose support for the Bush administration’s war in Iraq has put him at odds with grassroots Democrats.

According to poll director Douglas Schwartz: “Despite visits from former President Bill Clinton and other big-name Democrats, Lieberman has not been able to stem the tide to Lamont.”

That’s certainly the sense I’ve gotten on my visits to the state, as I’ve talked to Democratic voters who are furious with Lieberman’s neoconservatism and increasingly enthused about Lamont.

The prospect that the challenger might not merely win but win with by sizable margin is more important in this race than most.

Lieberman is planning to mount an independent run for the seat if he loses the primary. How far Lieberman can get as an independent will be decided by organizations such as the AFL-CIO, Planned Parenthood and the League of Conservation Voters — which have backed the incumbent because of his reasonably sound domestic record — and traditional Democratic donors. If the Democratic party’s 2000 vice presidential nominee is beaten badly in a homestate primary, it will be harder for him to get interest groups and big givers to stay with him as he mounts a sore-loser campaign in the fall.

Of course, the first task for Lamont is still to win — and, if he does, it will be a remarkable accomplishment considering the fact that the challenger was a virtual unknown six months ago. But if the first task is accomplished, then the question that will arise is: Did Lamont win by a decisive enough margin to get Lieberman to accept defeat in August rather than November?

Even a few weeks ago, a discussion about the size of Lamont’s margin would have seemed surreal. But this race has moved to a point where that discussion is becoming realistic — and consequential as regards the course of the fall campaign.