It's all legislative judo. The Repbublicans want this to go to a cloture vote, so that they they can force Democrat Senators who are up for re-election in 2014 to go on the record. Landrieu in LA and several other Democrats in red states are vulnerable, more so if they vote for gun control in states that have a large percentage of gun owners. If the bill gets cloture, it will go to a floor debate. Again, the Democrats will have to go on the record with their vote. If it passes in the Senate, it goes to the House. Where it will likely die. The House is much more granular, that is the districts represented by a Congressman are much smaller than the entire state represented by a Senator. While a Senator might get away with an unpopular vote, a Congressman is far less likely to.
Don't cite MA as an example of how Congressmen make unpopular votes and get re elected. This state is the exception, not the rule.
Gun control gave the Republicans the House in 1994 and the White House in 2000. If anything, sentiment against gun control is even stronger now than it was 20 years ago. Gun ownership is up, LTC and CCW permit requests across the country are way up. People want guns and they don't want restrictions, despite the lies that Shumer, Pelosi, and Obama are spouting on TV.