In our conversations with Chinese experts, the accumulation of these perceived changes in the U.S. position has led some of them to argue that China needs to take steps to make its red lines credible.

Chinese leaders would want to avoid war with the United States, but might be willing to risk an escalation such as challenging Ms. Pelosi’s plane or flying military aircraft directly over Taiwan for the first time. Inadvertent escalation would be a real risk.

In Washington, some experts think a crisis with Beijing over Taiwan is inevitable and that the United States should not back down. And Chinese leaders reflexively characterize almost all U.S. actions in support of Taiwan as dangerously provocative, creating the perception that Beijing’s dire warnings about Ms. Pelosi’s trip are mere bluster that can be ignored.

But neither side needs a war. And from a U.S. strategic standpoint, this is a particularly bad issue to pick a fight with China over: Even Democratic leaders in the executive and legislative branches are divided over Ms. Pelosi’s trip.