Cory Booker became the latest former presidential candidate to endorse Joe Biden, and our colleague Nick Corasaniti has the scoop.

Booker is planning to appear alongside Kamala Harris, who endorsed Biden on Sunday. Taking place ahead of the high-stakes Michigan primary, that event seems destined to take on a distinctly Klobuchar-and-Buttigieg-before-Super Tuesday feel.

Bernie Sanders got his own big endorsement from a black former presidential candidate — just not one from this election cycle. Jesse Jackson, whose own campaign in 1988 Sanders endorsed as mayor of Burlington, Vt., traveled to Grand Rapids, Mich., to endorse Sanders on Sunday. “I stand with Bernie Sanders today because he stood with me,” Jackson said to cheers. “I stand with him because he’s never lost his taste for justice for the people. I stand with him because he stands with you.” Revving up a crowd whose candidate’s chances have dimmed significantly in the past 10 days, Jackson led people in his trademark chant: “Keep hope alive!”

Sanders will need a lot more than hope if he is going to win Michigan, the big prize tomorrow, when nominating contests will be held in six states. On Super Tuesday, he failed to rack up enough support among liberals and white working-class voters to overcome his deep deficit among black voters in many states. And as Jonathan Martin and Astead W. Herndon point out in a new article, the 2018 Michigan governor’s race — in which a left-wing challenger was trounced by the moderate candidate, Gretchen Whitmer — offers yet more cause for concern for Sanders’s campaign.

Our eyes will be peeled today for the release of a Monmouth University poll of Michigan, expected by this afternoon.

As Democrats start to ponder who might be chosen as a vice-presidential nominee, with several of the former female presidential candidates frequently floated, the issue of gender remains front and center. In a story published this morning, Lisa Lerer and Reid J. Epstein explore the bitter aftertaste that is setting in for many Democratic women after the race narrowed to a battle between two white men.

“There must be a woman on this ticket,” Cecile Richards, a longtime abortion-rights activist and founder of the women’s organization Supermajority, told Reid and Lisa. “What is really important to see is representation, a commitment to the issues that women care about and a commitment to do something about it.”

During his remarks at the Sanders rally, Jackson made a pointed call to increase representation of black women in politics. “There is a great concern today about the impact of African-American women,” he said. “There should be one on the Supreme Court. There’s a real consideration,” he added, for a black woman “to be on the ticket of the next nominee of our party. Inclusion leads to growth, and with growth everybody wins.”

That is the central theme of a four-part documentary series on Hillary Clinton that Hulu released on Friday. The project began simply as an attempt to capture Clinton’s 2016 campaign on film, but it ended up as a four-hour documentary that tells the story of her life, and seeks to examine bigger questions about the treatment of female leaders in the public sphere.