That image is a meme going around social media right now, and a very dangerous one. Yes Democrats have a really good chance at winning back the Senate this year, but even if they do, there's a bigger chance they will lose it again come 2018 just because of how the cycles run. Bernie Sanders is one up for re-election in 2018 and considered a safe seat. But if Democrats try to push him to run as a Democrat and have Howard Dean primary him, they will be trying to replace a person with an 82% approval rating amongst his constituents with one that ended his career as governor at 42%. Not only that, but they will be replacing a man campaigning against lobbyists and big money with a lobbyist for the healthcare industry. Then there's the other pesky fact. Dean is one of the very few Democrats to have ever been endorsed by the NRA. Guess that kind of takes away from Hillary's attack on Bernie over guns. After all, he has never been endorsed by the NRA.
So basically some Democrats are pushing a tactic of cutting off the nose to spite their face, simple because they feel party loyalty is more important than party platform. And that right there is why Democrats keep losing.