... or don't introspect, blame the voters, and lose forever.
This is what frustrates me most about a lot of the left-leaning parties and voters I've encountered over the years. They think that "well obviously we should be winning, we're the good guys and they're the bad guys. People who vote against our position are either ignorant or evil. So we shouldn't change anything about it and we should ignore the people arguing against it."
Whether that's true or not isn't the point. The point is that you're not going to gain any more voters with that strategy. A lot of the people voting against the left have very real and tangible concerns, and you're not going to get them to vote for you by either telling them they're wrong to have those concerns or that they aren't even real in the first place. The left needs to provide them with real solutions to those problems.