to actually believe (and promote the idea) that the fate of the Democratic Party in ANY election cycle hinges on a single issue stretches the imagination beyond the breaking point. Secondly, gun control vs. unlimited gun rights is only a "big" issue to a very small percentage of Americans. A large majority of American voters, in fact, are in favor of enacting various forms of gun control legislation. The idea that ALL American gun owners vote as an "anti-gun control" bloc is a right-wing gun lobby lie, and is beyond ridiculous.
The Colorado recalls that the gun lobby touts so proudly was a fleeting victory. Two of those seats were re-claimed by Democrats in the 2014 elections, and the common sense Colorado gun laws enacted by Democrats remain on the books. The further assertions that the NRA was outspent and still "won," does not count the untraceable (Citizens United) Koch Bros/ALEC money that was funneled into Colorado in support of their puppet Republican candidates.
Support for gun control does not cost Democrats elections, but rather support for the right-wing gun lobby by "Liberals" who promote the "Democrats are coming for your guns" lie is a contributing factor -- but mainly voter apathy costs Democrats elections. If "gun rights" extremists would put as much effort into getting out the Democratic vote as they do when screaming about non-existent "infringement" of their gun rights, Democrats might win even more elections.
The Second Amendment absolutist gang would never vote for a Democrat in the first place, and to my mind that's a good thing. I, for one, do not want to be associated with them in any way.