What China might do to back up its threats if she does go to Taiwan is impossible to know from the outside. It’s also impossible to know from outside whether the Pentagon is justifiably alarmed or, as it has been in the past, reflexively cautious. Certainly over the past few months, Beijing has been more willing to run risks in challenging American and allied flights and naval operations in the area. Fueling the Pentagon’s caution further are undoubtedly worries that America’s very stretched, undermanned and underarmed military is also dealing with a military crisis on the other side of Eurasia. Even if Pelosi is underwhelmed by the briefing she is getting from defense and intelligence officials, she might still reasonably defer to the executive branch’s judgment that the time to visit Taiwan is not now since it is the executive branch that will be dealing with whatever does happen.

That said, the damage to American credibility in the region if Pelosi does not go are considerable. Beijing will have taken the measure of another American White House and found it to be more bark than bite.

There is no getting around the fact that there appear to be no obvious good choices here. It’s been suggested that the speaker can go at some other time, perhaps after the Communist Party Congress in late fall when there is less pressure on Xi to show a forceful hand. But Washington shouldn’t kid itself that this will make up for her decision not to go. It will be read in China, and perhaps elsewhere, as a sign that Beijing controls the “go” and the “no go” button on trips. In addition, China will have learned exactly what kinds of signals it can send to cause Washington to hyperventilate about a possible crisis. Upsetting that arithmetic may be reason enough for Pelosi to go.