. . . is the one you don't argue. And that, in a nutshell, has been liberalism's problem for many years. We seem to read too much into our setbacks; to adopt too readily the premises of our adversaries' arguments, and instinctively to go into a fetal position in the face of opposition. That may be changing, but it's changing too slowly, still.
Three cases in point: the 1980 elections; post-Bork, and post-assault rifle ban.
In 1980, the Democratic incumbent was one of the least popular presidents of the 20th Century. I happen to believe Carter was a much, much better president than anyone then and most people now give (or gave) him credit for, but there it is. He had fought a bruising fight to get the nomination and the late Ted Kennedy, admirable a man and a public figure as he was, was a terribly sore loser. His support for his party's ticket was lukewarm at best. The Democrats made the classic mistake with regard to their opponent - they treated Ronald Reagan as a joke. The politics of post-1965 America are strewn with the bodies of people who failed to understand that, while Reagan wasn't brilliant, he was a damned smart politician and he surrounded himself with even more smart politicians. Carter didn't help by conceding before the polls closed on the west coast (that wreaked more havoc among Democratic candidates for Congress than on the presidential race) and the networks piled on by declaring the election over some hours before it was actually over in California, Oregon, and Washington (or Hawaii and Alaska). Reagan won solidly and the Senate flipped to the Republicans for the first time since the early 1950s; senior Democrats in both houses were shown the door by their voters. That, at least, is the message Democrats took from the election. They bought into the "Reagan revolution" or at best opposed it tepidly, without stopping to think that 1980 might have presented unique circumstances that produced a unique result. And until 2008, Democrats fought elections on Republicans' terms using Republicans' definitions. The current debate on the debt "crisis" suggests Democrats still haven't completely learned their lesson.
Flash forward to the Bork nomination. The Senate was again in Democratic hands. Robert Bork was an idol among far-right legal types who falsely labeled him a scholar and a profound thinker. In fact, he was a RW political hack whose legal and political views were derived from the late 19th Century if not before that. He wasn't a scholar or a thinker, he was a polemicist. The Democrats' approach to his nomination was generally that of, "give a fool enough rope and . . .". The Republicans were sure that if Bork were only given a platform and the t.v. cameras, there would be a groundswell of new supporters, smitten as the 'pubs were by the man's sheer brilliance. And that is exactly what the Democrats did. They let Bork talk and talk and talk. The end result was, he lost two votes on the Republican side of the Judiciary Committee and his nomination was roundly defeated in the Senate. Then the Republican outrage about the shocking way Bork had been treated began. There was nothing shocking about it; the man was simply allowed to explain his views to the Committee and the television audience. A majority of the Committee and most likely a majority of the television audience didn't like what they heard at all. But the 'pubs ignored that possibility; they even developed a descriptive term for the outrage they wanted us to believe had been committed - "Borking". And damned if the Democrats didn't adopt it too! And of course, when the Clarence Thomas nomination came up, many of the Democrats on the Judiciary Committee, so determined to be "fair" this time (never mind that they had been fair the last time too) treated a thoroughly unqualified nominee whose sole two qualifications were his party affiliation and the color of his skin with kid gloves. They sat by while a credible witness against Thomas was really treated shabbily. And since that time, they really haven't given any Republican nominee anything near the kind of scrutiny a Democratic nominee is likely to face at the hands of the 'pubs.
Then, there was the assault rifle ban. It was enacted in 1994, the first Congress of Clinton's first term. In November of that year, the Democrats lost control of both houses of Congress. Some people fixed much of the blame on that bill (and gays in the military and the generally "freewheeling" style of the Clinton White House), not bothering to look at incredibly low Democratic turnout, even for a midterm election. Then Gore lost in 2000 (the NRA took much credit), so the Democratic politicians' urban myth became that, no matter what, the NRA cannot be beaten and shouldn't be opposed. Democrats were afraid even to make a vigorous case for regulating firearms and who gets to own them.
There is a case, a powerful case, as multiple appalling tragedies involving mass killings using firearms of various kinds have demonstrated. But until Democrats, particularly liberal Democrats are willing to stand up and make the argument, nothing is going to be done about it and if your next-door neighbor wants to fill up his garage with AK-47s and enough ammunition to fight a small war, well that's just too bad for you. This is, after all, America!