Long-term thinking like that doesn't work. There've only been two elections since the Reagan years where a plausible argument can be made that a marginally viable 3rd-party candidate affected the outcome of the presidential election: 1992 and 2000.
Yet the Overton window has still shifted radically rightward over the last 30+ years. The relatively paltry number of people in this country who have decided to vote for the candidate that best represents their values can hardly be blamed for that shift. It's a lot more plausible to blame the masses, especially those who lean to the left, who've decided to vote for centrist after centrist (i.e., "the lesser evil"), though the Republicans continue to nominate more and more radically right-wing candidates.
Democrats are like the Baltimore Ravens of politics. They load up with awesome, even inspirational defensive players and thus often rank highly in fewest points allowed, win a fair number of games as a result and go to the playoffs most years. Yeah, they might even win a Super Bowl. But mostly they lose the biggest games. Meanwhile the Manning brothers and Tom Brady lead teams to championship after championship.
Eventually you have to draft a QB a team can believe in.