Kamala Harris has done a remarkable job of consolidating the Democratic Party’s base of women and voters of color since President Biden dropped out of the race just over two weeks ago. She is now polling in a virtual tie with Donald Trump.

With her announcement on Tuesday that Gov. Tim Walz of Minnesota is her running mate, Ms. Harris has chosen a Midwest governor whose biography should give him an important opportunity to reach out to the male voters Democrats are struggling to reach.

There is no substitute for an energized base. But while that is a prerequisite to success, it is not sufficient for victory. For that Ms. Harris will almost certainly have to improve her numbers with a group of male voters whose drift away from Democrats predates her entry in this campaign.

As a former adviser to Hillary Clinton, I know all too well that there are some men who are reluctant to vote for a woman, and polling has made clear that young men in particular are increasingly backing Mr. Trump and the G.O.P. Ms. Harris can afford to lose this cohort. But she must cut into Mr. Trump’s margin.

It is clear that Ms. Harris understands this challenge — a key reason all of the top contenders for vice president were white and male, and why she was right to choose Mr. Walz.

All of the runners-up were impressive, especially Gov. Josh Shapiro of Pennsylvania, whose popularity and strong record in a critical swing state would have made him an excellent choice.

But only one is a former high school football coach: Mr. Walz. It’s an identity that has stuck over the years.