So, what gives? Does Biden know something that Senate Majority Leader Harry Reid, who, earlier this week, said that the assault weapons ban didn't have more than 40 votes, doesn't?
No. Biden knows the assault weapons ban won't pass. His insistence that it's not over until it's over is about two interrelated things: fighting until the end and showing gun rights advocates (and the liberal Democratic base) that he is fighting until the end.
To those who wonder why Biden is expressing optimism even in the face of almost-certain defeat, it's worth considering what his other options are. Imagine if Biden, the man who led the White House task force to develop the gun proposals and has served as the chief public cheerleader for the effort, publicly walked away from the assault weapons ban. The outcry from the liberal left, which is already unhappy with Reid for not at least attempting to include the assault weapons ban in the broader package, would grow to epic proportions -- with the base insisting that Democrats gave up without a fight.
Biden is mindful that simply because a quest is quixotic doesn't render it meaningless. The vice president has been open about his interest in running for president in 2016 and he is well aware that championing a cause that is near and dear to the hearts of many liberal activists is a political winner -- whether or not that work yields the desired results.
What Biden is doing is casting himself as the last man standing on the assault weapons ban, the person least willing to walk away from what he believes is the right thing to do. That's a good place to be if you are a Democrat who wants to run for president in three years time. And Biden knows it.