But it would not take a far-fetched string of events for this to go horribly wrong. What if public sentiment turned against Mr. Newsom for whatever reason, a Republican won and something happened to one of the state’s Democratic senators? The health of Dianne Feinstein, who turns 88 next month, has been the subject of much concern. The new governor could appoint a Republican replacement, upending Democratic control of the U.S. Senate. Is that a risk Democrats are willing to take, to protect Mr. Newsom by keeping Democratic alternatives off the ballot? Perhaps the risk will seem very small when the deadline to enter the race arrives, 60 days before the election. But there is no shortage of ambitious Democrats for whom a late entry might prove attractive, including ones with both name recognition and access to the money necessary to wage a credible campaign. Like Representative Adam Schiff, who recently lobbied the governor unsuccessfully to be appointed the state’s attorney general and raised more than $40 million in 2020. Or Lt. Gov. Eleni Kounalakis, who became the first woman elected to the post, in her novice run for office, aided by more than $10 million from herself and her father, a real estate developer. For now, they have all pledged allegiance to Mr. Newsom, whose campaign has orchestrated displays of pointed unity, suggesting that any Democrat who broke ranks would be nothing short of traitorous. It is hard to see how that unity will hold. Or how it can be justified as being in the best interests of the Democrats, or the democracy. But Mr. Newsom has had something of a charmed existence in his political career, and perhaps his luck will hold.