Until Donald Trump’s tweet tirade against the “Squad,” I was getting pessimistic about the chances that Democrats could overcome their divisions for the 2020 election. Now, at least for the moment, Trump has solved that problem—nothing unifies Democrats better than a racist and xenophobic attack. But I’m even more concerned about how Trump continues to dominate the framing of America’s choices in 2020.

This is an election that ought to be about the climate emergency facing America and the world. It ought to be about the continuing economic insecurity of families at a time when the gains from growth—and from Trump’s tax cuts—flow overwhelmingly to the rich. It ought to be about the affordability of housing, health care, education, and other basic needs.

The election ought to be about the corruption that Trump has brought to Washington, his abuse of presidential powers, and the risk he poses to constitutional norms and democracy. It ought to be about the encouragement that Trump has given to authoritarians around the world, his embrace of Vladimir Putin, Viktor Orban, and Rodrigo Duterte, and the decisions he has made to withdraw the United States from arms control treaties and increase the risk of a new global arms race.

Perhaps most of all, the election ought to be about the likelihood that right-wing power will become entrenched if Trump wins a second term, with consequences stretching far into the future. The Supreme Court could go from a 5-4 to a 7-2 conservative majority, make radical rulings that stand for decades, reverse civil rights and other protections for racial and gender equality, and severely weaken the powers of the federal government in dealing with environmental risks, economic inequality, health care, and other challenges.

But if Trump has his way, no one will be focusing on those concerns. This will be an election in which the politics of fear and divisions over race and immigration dominate the national conversation.

Provoking outrage has been Trump’s strategy for years, and it has worked for him. His championing of birtherism put him on the road to power. Every time he stokes the fires of racism and xenophobia he puts Democrats in an impossible position: Ignore what he says at the risk of normalizing it, or answer back and allow him to define the terms of conflict.

Democrats are especially vulnerable just now. With the presidential nomination race wide open, they are effectively leaderless. Trump is taking advantage of that void to make the Squad the faces of the Democratic Party, calculating that they are the perfect symbols to drive his voters to the polls.

Some of the leading 2020 Democratic presidential candidates didn’t help their cause in the June debates by taking a series of unpopular positions, such as banning private health insurance, providing insurance to the undocumented, and decriminalizing border entry. They’re giving Trump and the Republicans plenty to work with.

There’s a real danger of Democrats getting ahead of themselves. Eventually, they should benefit electorally from the rising numbers of people of color and a younger generation with progressive views. But that emerging majority isn’t a majority of voters yet, and the sense that it is on the way is creating a panic among conservative whites. That’s one reason why white conservatives vote at so high a rate. In an article in The Atlantic last month, “The Electoral Time Machine That Could Re-Elect Trump,” Robert P. Jones points out that even as the proportion of white evangelicals in the population has fallen, their share of voters hasn’t. They dropped from 21 percent of the population in 2008 to 17 percent in 2016, but their share of the voters remained constant at 26 percent.

Moreover, Democrats can’t count on that rising new electorate because the presidential election will be decided in a handful of states, including the states in the Midwest with older, disproportionately white populations that gave Trump a victory in the Electoral College in 2016.

Once the Democratic nomination race is resolved, the party’s presidential candidate will be in a better position to define what the campaign and election are about. But that may not be for a long time because of the fragmentation of support among candidates in the primaries and the possibility that the race will go all the way to the convention.

In the meantime, the candidates need to avoid getting caught in Trump’s trap and do everything possible to turn attention back to the real stakes in the election. This has become a crucial test in the Democratic race: Who can compete most effectively in the attention market against the country’s master of outrage, chaos, and distraction? If Trump dominates what Americans are thinking about for the next year, he will have already won a big victory before the votes are tallied.