As a College Student and NM Resident, I find it EXTREMELY unlikely that Sen. Bingaman will retire in 2006.  If he runs for reelection, he wins with about 65% of the vote! If he retires, (he won't) then Democrats seem to have a problem:
Rep. Heather Wilson (NM-1) would easily win the Republican nomination - NM doesn't have a deep Republican bench.  Now, she wouldn't face Gov. Richardson (who is futilely trying to run for President - or VP in 2008) and would easily slaughter Lt. Gov. Denish.  That leaves a countless number of nominally popular Democrats holding any number of state-wide positions.  There is Rep. Tom Udall (NM-3) who would lose, and is wise enough to not run.  So who do Democrats put up to bat?  Not any Judges.  Unlike Texans, New Mexicans like to keep separate their three branches of government.  Albuquerque has an inept Dem Mayor, and big Dem names (i.e. Maloof and King) are on a sustained losing streak.  
I think that NM Democrats' best bet is Kari Brandenberg, District Attorney for Bernalillo County (NM's most populous county).  She is a popular go-getter who would give Heather a run for her money... then again if Heather runs, Brandenberg may want her seat, and if NM-1 is an open seat, Brandenberg should win in a landslide against almost any Republican.
Democrats - hope that Bingaman doesn't retire.  Republicans - hope that he does, but add depth to your political bench ASAP!!!