What to Know About Night 3 of The Democratic National Convention

After two nights of preliminary revels that laid out Joseph R. Biden Jr.’s biography and the values of his party, the Democratic Party turns on Wednesday to forging its ticket in earnest. Senator Kamala Harris, the vice-presidential nominee, is the headline speaker of the night, giving remarks that will introduce her to a national electorate that still only has a modest familiarity with her political identity and ideas.

It is a crucial speech not only for Ms. Harris but for the whole Democratic general-election effort. It will be the first opportunity for Americans to hear from someone who is actually asking for their vote on the national ballot about what a Biden-Harris administration aims to achieve. With a few exceptions so far — including Senators Bernie Sanders and Chuck Schumer — Democrats have not gone into much detail about how a government led by their party would change the lives of ordinary people.

But Ms. Harris will not have to fill in those blanks by herself. Two of her party’s best-known leaders, and most fluent policy representatives, will be speaking before her: former President Barack Obama and Senator Elizabeth Warren. Both have leaned hard into a message of sweeping economic and social change — Ms. Warren during her presidential bid, Mr. Obama in a number of recent public remarks — and they are likely to help the party clarify its governing aims in a way it has not yet done this week.

Wednesday’s lineup

Kerry Washington, who recently received four Emmy nominations, follows in the footsteps of Eva Longoria and Tracee Ellis Ross as tonight’s M.C.