Even the New York Times has come to realize what we all knew a long time ago. Hillary Clinton really believed that she was inevitable during this election cycle, and she failed to take Bernie Sanders seriously.

Mrs. Clinton and her team say they always anticipated the race would tighten, with campaign manager Robby Mook telling colleagues last spring that Mr. Sanders would be tough competition. Yet they were not prepared for Mr. Sanders to become so popular with young people and independents, especially women, whom Mrs. Clinton views as a key part of her base.

Given her many political advantages, like rich donors and widespread support from Democratic Party elites, she is also surprised that Mr. Sanders’s fund-raising has rivaled hers and that her experience — along with her potential to make history as the first woman elected president — has not galvanized more voters.

“It was probably never going be a straight line — we hoped it would be but feared it wouldn’t be,” said James Carville, the Democratic strategist on Mr. Clinton’s 1992 campaign and a longtime friend of the Clintons. “She’s performed solidly enough, but it’s been a hard race.”

Several Clinton advisers are also regretting that they did not push for more debates, where Mrs. Clinton excels, to more skillfully marginalize Mr. Sanders over his Senate votes in support of the gun industry and the enormous costs and likely tax increases tied to his big-government agenda.

Instead, Mrs. Clinton, who entered the race as the prohibitive favorite, played it safe, opting for as few debates as possible, which were scheduled at times when viewership was likely to be low — like this Sunday at 9 p.m. on a long holiday weekend.

So, with weak poll numbers in Iowa and New Hampshire nearly lost, it’s time for a strategy change. Target: Bernie. And one of Hillary’s opening salvos was about as backhanded and jaw-dropping as possible.