Liberals who are indulging these sentiments should reflect on the fact that conservatives, when they are frustrated about politics, have parallel beliefs. Unhappy Republicans blame defeats on Republicans who were too nice for their own good. One popular theory on the right holds that President Donald Trump won his election while Mitt Romney lost his because the latter never went for the jugular. (The differing results probably had more to do with the opponent each man faced.)
Conservatives say that the system is stacked against them, too, albeit in different ways than liberals allege. The media, the universities, Hollywood and, now, the "deep state" are what thwart conservative victories, while gerrymandering, the Koch brothers and outdated constitutional structures are what stymie liberals.
The existence of mirror-image thinking among conservatives doesn't prove that the progressives' complaints are wrong. But there are two mistakes that dissatisfied Democrats should avoid making.
The first is to assume that they speak for most of the country. Once you've made that assumption as both liberals and conservatives often do setbacks become proof of a nefarious plot to foil the people's will. At the same time, persuasion of people who aren't already in your camp becomes unnecessary.
The popular-vote plurality for Hillary Clinton has helped to feed this illusion on the left. So have polls in which majorities, sometimes large ones, appear to agree with liberal positions.
The truth is, though, that Clinton won a lot of votes from people who distrusted her but were more repelled by Trump (just as a lot of his voters had major reservations about him). And polls can be misleading. While it is true that most Americans favor certain new regulations on guns, for example, it doesn't mean that they share liberals' passion for them.
Another mistake is to underestimate how political actors would adapt to new rules.
Let's say liberal activists succeeded in abolishing the Electoral College and the equal representation of states in the Senate. All else equal, you'd expect government policies significantly to the left of the ones you have under the current arrangements, which boost the political power of rural and exurban conservatives. But I would not necessarily expect Democrats to become an enduring majority party as a result.
At least as likely is that Republicans would move a little bit left and stay competitive. They would still be able to win presidential and Senate elections, and to appoint justices of the Supreme Court who would infuriate millions of people on the port side of the (newly re-centered) political spectrum. Liberals might not even be any happier, since their sense of the victories to which they are entitled would also adjust to the new rules.
Speaking of adaptation, liberals have it within their power to do better under the current arrangements, too.
If Clinton had made the minimal efforts that previous Democrats had made to signal that she respected voters' concerns about illegal immigration or religious freedom she might well have won the 2016 election. She didn't, in large part, because a lot of Democrats had convinced themselves they represented a "coalition of the ascendant." And when you already have the people on your side, you don't have to persuade the people you don't.
Many progressives have ideological objections to the federal structure of our government, and when principle and interest line up political movements will follow. But it wasn't the constitutional rules or Democrats' manners that put them in the political wilderness. It was their own choices.