My guess would be that the Dems won seats in 2006 and thought it was a mandate. Committee chairman had been around when the first went through and saw that they lost control for over 10 years. Not wanting to face that again they tabled it.
Moderate Republicans wanting to regain control thought that if they sponsored a bill the Dems would fall all over it. But being an election year and Heller before the SCOTUS they just left it alone.
Now with the Dems controlling the House, Senate and White House I'd bet that they think NOW will be as good a time as ever. But if they value their job they'd leave it alone and do something good for this country first. But some idiot will try it again just because that's all they know.
