Almost as soon as the massacre at the Orlando nightclub Pulse ended, Democrats took up their push to forbid people on the terrorism watch list from purchasing guns.

The timing, in the wake of the awful shock of the Orlando attack, was right, and the talking points wrote themselves. The polling was, of course, very good. The only problem was that the Orlando killer wasn’t on the watch list when he bought his weapons (although he had previously been on the list in 2013 and 2014 before the FBI removed him). Democrats nonetheless maintained that the watch-list legislation was an urgent necessity.

Few policy proposals are as routinely irrelevant as so-called common-sense gun-control measures — and seemingly, the less relevant they are, the more passionately their advocates support them. The three proposals that the left always calls for — prohibitions of purchases by people on the watch list; ending the alleged gun-show loophole; universal background checks — usually have nothing to do with the shootings they are meant to stop. They are a trinity of non sequiturs.

Consider the Orlando and San Bernardino killers. They weren’t on the terrorism watch list when they bought their guns; they didn’t go to gun shows to get them; and they all passed background checks. Democrats could have passed their preferred legislation on all these matters long ago, and it wouldn’t have discomfited these monsters in the least.

When asked about this by ABC journalist Jonathan Karl on “This Week With George Stephanopoulos,” Sen. Chris Murphy of Connecticut, the Democrat who took to the Senate floor to filibuster for gun control last week, brushed it off. “We can’t,” he explained, “get into the trap in which we are forced to defend our proposals simply because it didn’t stop the last tragedy.”

The question of effectiveness shouldn’t be considered a “trap,” but rather a basic measuring stick of legislation. It’s hard to think of any other area where a political party is so thunderously self-righteous while not caring whether its proposals would materially change anything or not.

In light of the fact that Omar Mateen had once been on the terrorist watch list, Democrats widened the net of their proposed legislation to catch not just people who are on the list, but have been investigated during the past five years. This implicit nod toward relevance makes the central flaw in the bill worse: It would deny people a constitutional right based on mere suspicion, with no real opportunity for due process. (It should be possible to reach a compromise that includes some reasonable measure of due process, although none seems in the offing for now.)

Everyone understands and feels the impulse to do something after the horror of Orlando — and we should do all we can to crush ISIS and thwart its sick propaganda and recruitment campaigns — but gun control simply isn’t a good tool for fighting terrorism.

What the Democrats really want is symbolic victories against gun ownership and the gun culture, which they loathe. Their instinct was to make Orlando as much about the NRA, and as little about ISIS, as possible.

It is telling that one of the more sweeping gun-control measures of the past 30 years, the since-lapsed assault-weapons ban, had to do less with the functionality of the prohibited guns than their cosmetic features. It was a victory for show (and had little or no effect on gun violence).

Since their current gun-control agenda isn’t going to make a practical difference, Democrats might as well try to shift the terrain of the debate by working to make proposals for a wide-ranging gun ban and confiscation more mainstream. The politics would be (deservedly) treacherous, and any such measures would run afoul of the Second Amendment, but at least the stakes would match the Democrats’ passionate intensity.

The risk, though, is too much for them. Which means they will almost certainly continue their irrelevant crusade.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.