I'm surprised so many think Democrats have the losing message with gun control.
It's not. They should talk about it a lot more.
An overwhelming per cent of voters support the Democratic position of sensible gun control.
Voters in narrowly Democratic states like Maine and Nevada oppose background checks in referendums, which is like the most milquetoast gun control suggestion around. Pretty clearly a majority of Americans just disagree with Democrats on this issue (much as a majority of Americans disagree with Republicans on abortion, actually).
Also much like abortion, this isn't an issue most of the time; Republicans successfully made it more of an issue than usual in the 2014 midterm (and both parties collaborated to bring it to the forefront in the 2000 election), but that was unusual. If it is an important issue, it will tend to help Republicans; if abortion is, that will tend to help Democrats.