I put all these scorecards in an Excel and sorted by Party and found the averages and then I took the 18 DLC Senators (listed below) to find their average. There is a substantive difference between the GOP and all Democrats on these issues. I have seen the union scorecards and know there is substantial difference on that as well, just haven't crunched the data yet (actually, on the SEIU scorecard for last year, all 18 DLCers scored 100% but there were only three votes recorded).
Oh, and I included Jeffords in with the Dems (he caucuses with us).
NEA 2004 Congressional Scorecard
http://capwiz.com/nea/scorecard/?chamber=S&session=108&x=15&y=13GOP AVG 29
DEM AVG 88
DLC AVG 90
2004 League of Conservation Voters (LCV)
http://www.capwiz.com/lcv/dbq/vote_info/?offset=0&length=40&session=108&chamber=S&command=results&sort=Last&state=GOP AVG 11
DEM AVG 74
DLC AVG 65
2004 NARAL
http://www.vote-smart.org/issue_rating_detail.php?sig_id=003432M&sort=currentofficeGOP 5.9
DEM 81.5
DLC 68.9
2004 ACLU
http://action.aclu.org/site/VoteCenter?page=congScorecard&congress=108&location=S&lcmd=next&lcmd_cf=GOP 13
DEM 68
DLC 67
NEA:
DLC
Mark Pryor (D) 85% 85%
Max Baucus (D) 85% 85%
Hillary Clinton (D) 85% 85%
Herbert Kohl (D) 85% 85%
Thomas Carper (D) 85% 85%
Joseph Lieberman (D) 88% 88%
Blanche Lincoln (D) 90% 90%
Dianne Feinstein (D) 90% 90%
Bill Nelson (D) 90% 90%
Evan Bayh (D) 90% 90%
Mary Landrieu (D) 90% 90%
Ben Nelson (D) 90% 90%
Kent Conrad (D) 90% 90%
Tim Johnson (D) 94% 94%
Debbie Stabenow (D) 95% 95%
Byron Dorgan (D) 95% 95%
Maria Cantwell (D) 95% 95%
John Kerry (D) 100% 100%