Bill de Blasio is mayor of New York.

Like many Democrats, I’ve spent a lot of time since Nov. 8 wondering what went wrong. Though Hillary Clinton won the popular vote by nearly 3 million votes, it’s clear to me that too many voters stayed home because they felt the election was more about personalities than the issues that affect their lives.

But what we’ve seen in the days after the inauguration is nothing short of incredible. All over the country, millions of people are getting organized and demonstrating against the president and the broken policies of the Republican Party. People are starting to feel their power to stop the administration.

The new mission of the Democratic Party must be to harness and build on this energy. We need determined leadership that will bring us together as one united party. We need an inspiring vision of equality that resonates in the hearts, minds and souls of all Americans. We need to renew our commitment to strengthening our grass-roots infrastructure to take on President Trump and the Republicans.

You’d be hard-pressed to write a better description of Keith Ellison’s approach to public service. That’s why I’m supporting him in the race to be the next chairman of the Democratic Party.

[Keith Ellison: ‘The Democratic Party doesn’t exist for Democrats’]

As leader of the Congressional Progressive Caucus, Keith, a Democrat from Minnesota, has been fighting to put working families at the center of our economic vision. He has built coalitions to raise wages for federal contract workers and stop cuts to Social Security, Medicare and Medicaid. If there’s a strike happening, you can almost guarantee Keith will be there right next to the workers.

And beyond being right on the issues, Keith knows what Democrats need to do to win.

During his successful run for Congress in 2006, his campaign knocked on doors and talked to voters who were neglected for years. That shaped Keith’s approach to winning elections. He built a turnout machine in Minnesota by contacting as many voters as possible. It helped elect statewide Democrats in critical election years, including Sen. Al Franken’s win by 312 votes in 2008. Surrounded by red states, Minnesota continues to shine blue in part thanks to voter participation levels that often lead the nation.

Nationwide, 58 percent of eligible voters went to the polls in 2016. A larger focus on turnout in key states might have changed the outcome. That’s why Keith’s experience and his plan to build a 3,143-county turnout strategy is so important. He wants local and state leaders to boost their turnout by 3 to 7 percent. He is committed to make that happen by shifting the resources of the Democratic Party toward a grass-roots focus on getting voters to the polls. Higher turnout everywhere means victories not only at the federal level but at the state and local levels as well.

Keith also knows Democrats go further when we go as one. While the people in our party don’t agree on everything, Keith knows it is our shared values that animate us to do good, fight for progressive values and lift up our fellow Americans. At the Democratic National Convention, I watched Keith, who had endorsed Sen. Bernie Sanders (I-Vt.), barnstorm state delegations urging party unity for Democrats to rally behind Hillary Clinton. Later, he went to Nevada to facilitate a meeting between Sanders supporters and the Nevada Democratic Party leadership, helping to deliver a public unity statement after a contentious state convention in May.

No matter what the president says about “draining the swamp,” Republicans will continue to be the party of millionaires and billionaires. I expect the GOP to break its promises to the people who supported it in the fall because they felt left behind economically. When that happens, the Democratic Party will have a big opportunity to win over some of the voters we lost.

But what we learned from the 2016 election is that being right on the issues isn’t enough to win those voters back.

[Obamacare’s enduring victory]

The campaign last year became too much about the wrong thing. It focused on what was bad about Donald Trump — his character and his personality. But we should’ve been focused more on what we could do to put more money in the pockets of working Americans.

Ironically, that was exactly the focus of our party’s primary process. Clinton and Sanders spent months debating who could do more to lift up working families. The debate was substantive and high-minded. It brought new people into the process, introduced ideas that didn’t seem possible just a few years ago and, most important, energized our party.

We now need to do the hard work of harnessing that energy. We need to organize year-round to constantly remind people that we stand for them. We have to live our values and focus on small-dollar donations. We need to show the voters left behind by Trump’s tax cuts for the wealthy and corporations that our party represents them and that we’re beholden only to them. We’ve got to give them a reason to go to the polls.

Trump likes to say he built a movement. The demonstrations around the country prove there’s a people-powered movement ready to fight against him and the Republican Party. I believe Keith is the leader we need to build a party capable of channeling that power to win up and down the ballot.