Donald Trump’s address to Congress took an optimistic and conciliatory tone, a welcome departure from the combative style of his inaugural address and the dystopian nation he had sketched out.

The content was more notable still. The word debt appeared once. The budget deficit was not mentioned at all. If there was any doubt that the president wanted to spend an immense amount of money, while cutting taxes, the speech obliterated it. His own party, which controls Congress, may stick to principle and resist. It can expect Democratic help if it does so. Republicans have abandoned fiscal conservatism in the past — when they held the presidency. But to sign on to deficit spending of Trumpian breadth and scale would be unprecedented.

Legislative progress of any kind depends on the administration abandoning the pointlessly belligerent tone of its early days. The speech, directed mainly at a domestic audience, was a step in that direction. Opening with acknowledgment of recent anti-