I was never been surprised that Lamont was competitive in this case. Lieberman is an endangered species in democratic politics - an unprogressive democrat in a liberal blue state - and just for good measure he flaunted it. Over the last 20 years, two distinct types of democrats have emerged, "moderate" DLC democrats, and "progressive" liberals. This difference largely exists out of electoral necessity. Its very difficult for progressives to be elected to elected in red states, and DLC dems are out of touch with the democratic base in blue states. As more elections have taken place and more incumbents have retired, this trend has accelerated.
I've used progressive punch's ratings - you may not agree with them, but they are good enough to highlight this divide.
Now, I've arbitrarily decided that 85% = a good progressive. Here are the 24 Democrats who scored over an 85.
1D 96.90 Sarbanes, Paul S. D MD
2D 96.68 Reed, Jack D RI
3D 95.68 Kennedy, Edward M. D MA
4D 95.09 Boxer, Barbara D CA
5D 94.39 Durbin, Richard D IL
6D 92.96 Menendez, Robert D NJ
7D 92.92 Levin, Carl D MI
8D 92.54 Lautenberg, Frank R. D NJ
9D 92.37 Obama, Barack D IL
10D 91.54 Clinton, Hillary Rodham D NY
11D 91.13 Akaka, Daniel K. D HI
12R 91.09 Harkin, Tom D IA
13D 90.75 Leahy, Patrick J. D VT
14D 90.45 Stabenow, Debbie D MI
15D 90.36 Schumer, Charles E. D NY
16D 90.24 Murray, Patty D WA
17D 89.91 Dayton, Mark D MN
18D 89.76 Mikulski, Barbara A. D MD
19D 89.19 Feingold, Russell D. D WI
20D 88.31 Cantwell, Maria D WA
21D 88.00 Wyden, Ron D OR
22D 87.16 Dodd, Christopher J. D CT
23D 86.37 Kerry, John F. D MA
24R 86.03 Rockefeller, John D., IV D WV
You can see that 22 out of 24 progressives are from Blue states, and that the two other states are red states that were once blue
. If we look at the remainder of the democrats - who had below 85%...
25D 84.67 Biden, Joseph R., Jr. D DE
26D 84.14 Feinstein, Dianne D CA
27R 83.22 Dorgan, Byron L. D ND
28R 82.55 Johnson, Tim D SD
29D 81.82 Kohl, Herb D WI
30R 81.78 Nelson, Bill D FL
31D 81.76 Inouye, Daniel K. D HI
32R 81.61 Bingaman, Jeff D NM
33R 81.53 Reid, Harry D NV
34R 81.05 Salazar, Ken D CO
35R 79.87 Bayh, Evan D IN
36R 79.21 Conrad, Kent D ND
37R 78.27 Byrd, Robert C. D WV
38R 77.36 Pryor, Mark L. D AR
39D 76.41 Lieberman, Joseph I. D CT
40D 74.47 Carper, Thomas R. D DE
41R 74.41 Landrieu, Mary L. D LA
42R 74.38 Lincoln, Blanche L. D AR
43R 72.66 Baucus, Max D MT
44R 47.62 Nelson, E. Benjamin D NE
We can see that only 6 out of these 19 less progresive democrats are from blue states. We can further note that of the 15 red state democratic senators, only two are above the arbitrary 85% line.
Now, we can also see that past 81% or so... blue state democrats seem to be totally replaced by red state dems, just as by 85% there are no longer many red state dems left. This seems to indicate that the 'center' of the democratic party is between about 81-85% on progressive punch.
Given this, lets look at those who are right of the democratic center...
32R 81.61 Bingaman, Jeff D NM
33R 81.53 Reid, Harry D NV
34R 81.05 Salazar, Ken D CO
35R 79.87 Bayh, Evan D IN
36R 79.21 Conrad, Kent D ND
37R 78.27 Byrd, Robert C. D WV
38R 77.36 Pryor, Mark L. D AR
39D 76.41 Lieberman, Joseph I. D CT
40D 74.47 Carper, Thomas R. D DE
41R 74.41 Landrieu, Mary L. D LA
42R 74.38 Lincoln, Blanche L. D AR
you'll note that there are only two blue state dems left - Lieberman and Carper.
Now usually, these dems will survive until they end their careers and they will be replaced by a progressive democrat.
In that sense, Lamont was inevitable. Ultimately, a state as liberal as CT was going to have a progressive senator. However, Lieberman, by flaunting his centrism and deriding the progressives which constitute a majority of his "base", managed to bring an early exit upon itself.
Thus we can further conclude that Lamont's victory does not constitute a shift to the left in the democratic party. Blue States have had liberal senators for years, and the fact that a liberal state would choose to have a liberal senator is FAR from absurd. The fact that this occured is a testimant to Liebermans own arrogance - his willingness to both boldly proclaim that he was out of touch with his party, and then further insulted liberals in more offensive ways - not that the party itself shifted.