The tweet of the year — we understand the year is young, but, hey, it’s all we’ve got — has to be @realDonaldTrump’s heads-up to Congress. “Media Posts,” it says, “will serve as notification to the United States Congress that should Iran strike any U.S. person or target, the United States will quickly & fully strike back, & perhaps in a disproportionate manner. Such legal notice is not required, but is given nevertheless.”

So here’s the question. Which is causing more consternation on the World Wide Web? Is it the substance of Mr. Trump’s tweet, the news that the Congress is being informed that America will respond to any strike by the ayatollahs? Is it the substance of the warning that the response by America might be disproportionate? Or even the claim that such notice isn’t required under the War Powers Act?

Or is it the consternation being caused by the fact that the President is parleying with — or at least at — Congress not in the more formal medium of, say, the letter or even, say, a telegram or an email but in the truncated medium of the tweet? That is, is the medium to which the President has resorted in getting word to Congress — that is, the tweet — the real message of the tweet in the first place?

Where is Marshall McLuhan when we need him? He’s the Canadian sage — media theorist — who came up with the formulation that the medium is the message. A newspaper is not a philosopher, but we’re of the impression that McLuhan had the notion that the medium could be even more important than the message. We haven’t heard a lot about that theory lately, which may owe to the fact that McLuhan died in 1980.

It’s hard, in any event, to think of a moment in our national politics in which the medium is more likely to be the message than in Mr. Trump’s tweet to Congress in respect of Iran. It carries a certain jaunty air, unbefitting — in our view — not only a message to Congress on any subject but particularly a message to Congress in respect of war. People have already died, after all, and many more may yet die.

Then again, too, maybe we’re wrong. The reactions on Capitol Hill to President Trump’s decision to go after the Iranian terror master Qassim Soleimani have been shockingly solipsistic. One Democrat has fretted about being left in the dark. One after another has criticized the president or even spoken of the Iranians as if they are the victims of an unprovoked attack. They have fretted about war.

Not one single Democrat — not even Speaker Pelosi, say, nor Senate Minority Leader Schumer, nor the Intelligence Committee chairman, Congressman Schiff — has asked how he or she could help win the war. The issue that seems to obsess the Democrats seems to be protecting not our own troops but Congress’ own turf and rattling on about how escalatory and reckless the President has been.

In that case, it may be that the President is choosing his medium as carefully as he seems to be choosing his words. Maybe he’s not in a mood to deal with Congress through the stately medium of stationery and quill. Maybe he’d prefer to wait for a more discursive moment to do that — a State of the Union address, say. Then again also, too, he was upstaged at the last one by the Speaker’s own patented medium, the Pelosi Clap. The medium seems to be the message, indeed.