Bingaman (D NM) was a safe seat for democrats. He is now out of the 2012 race. Source.
The seat goes from safe Dem to toss-up at worst. It is more likely “likely” republican at this point. Many republicans have talked about Heather Wilson (former congresswoman) as a strong potential, with a couple of businessmen in the mix as well.
The 2012 senate race is already heating up, with the republicans taking the senate (with seats to spare) if the elction were held today. Unless the dems change the political climate today, they are defending 33 seats to 10 for the GOP, and mostly in states the GOP is strong in (such as those who voted against Obama).