David Axelrod, the political strategist who guided Barack Obama to the White House, has a theory. Presidents, he says, are followed by their opposites. “Voters rarely seek the replica of what they have,” he’s written. “They almost always seek the remedy, the candidate who has the personal qualities the public finds lacking in the departing executive.”

And so the cautious, patrician George H.W. Bush was succeeded by the charismatic, empathic Bill Clinton; Clinton's freewheeling, libertine style opened the way for George W. Bush’s religious, moralistic appeal; W's folksy, divisive nationalism led to Barack Obama's cerebral cosmopolitanism. And Donald Trump? His nostalgic, revanchist populism is a neck-snapping reversal of his predecessor’s politics. "He is the antithesis to Obama," Axelrod told me back during the campaign.

Which raises a question. What — or, more precisely, who — is Trump’s opposite?

Two different theories are emerging in two of the Democratic Party’s most interesting leaders. I’ve recently interviewed Sens. Elizabeth Warren and Cory Booker (both conversations are available, in full, on my podcast), and have been struck by the contrast in their responses to the Trump era.

Elizabeth Warren: Democrats have to become what Trump only pretends to be

Warren, whose new book is titled This Fight Is Our Fight, believes the antidote to Trumpism is an authentic, liberal populism. In her view, Democrats must become the thing Trump only pretends to be — warriors against the rich, powerful interests that have overwhelmed American democracy.

“I actually do think the fight metaphor is right,” she told me when I asked whether Trump’s angry faux-populism could only be countered with an angry real populism. “This is how democracy works now ... everything we hold dear is truly under assault.”

To Warren, being in a fight means, well, fighting. She has been rare among national Democrats in attacking Trump in much the terms that Trump attacks everyone else. This is, for her, a calculated choice — and one she made with considerable unease. In her book, she recalls receiving a forwarded email from a friend of a friend. “What is our senator doing rolling around in the mud with Donald Trump?” it said.

Let’s be honest - @realDonaldTrump is a loser. Count all his failed businesses. See how he cheated people w/ scams like Trump U. — Elizabeth Warren (@elizabethforma) March 21, 2016

“No kidding,” writes Warren. “I knew just how she felt. But Trump could be closing in on the presidency, and those tweetstorms and Facebook posts caused millions of people to tune in — at one point, about 46 million people were following these exchanges. I figured that if tweeting and posting and poking and prodding gave me a chance to reach millions of people, then that’s what I should do. Some of those people might not have heard that Donald Trump cheated his workers or defrauded students. Some of them might decide that Donald Trump was not going to fight for them.”

To Warren, this is what it’s all truly about. Who will fight for you? “The game is rigged,” she writes. “It is deliberately, persistently, and aggressively rigged to help the rich and powerful get richer and more powerful.”

Warren offers one vision of how the Democratic Party should respond to Trump: They should recognize the fight is vicious and existential, and they must make clear which side they’re on. In her view, the antidote to Trumpism is found in the gap between his promises and his policies. His populism is fake. Democrats’ populism must be real. Trump’s policies help the rich and the powerful. Democrats’ policies must help the poor and the powerless. Trump is running a government filled with Goldman Sachs appointees. Democrats should break up Goldman Sachs.

But above all else, for Warren, this is the difference: Trump fights for himself. Democrats need to show they will fight for you.

Cory Booker and the politics of love

If Warren thinks Democrats need to become what Trump merely claims to be, Booker believes they need to become what Trump clearly isn’t. In his view, the opposite of Trump’s angry, resentment-fueled politics is a compassionate, love-fueled politics. The opposite of a president who makes politics feel like a war is a politician who at least carries the possibility of peace.

“I really believe this is the response to the era of Donald Trump, and I’m sorry if it sounds corny, but I don’t think it’s corny at all,” Booker says. “It’s gotta be about love. it’s gotta be about the connections we have to each other.”

Like Warren, Booker is uncomfortable with the attacks he’s launched on Trump. But unlike Warren, he thinks his discomfort is a strength, not a weakness. “I called Donald Trump a liar on national TV, and when I got off TV, I felt bad, because it violated my values,” he says. “I can say he was lying, which is the right thing to do, because he did lie, and he does lie quite often. But I didn’t like to be crossing a line and condemning his soul.”

The point, Booker continues, is that Democrats “cannot become what we are trying to replace.” He likes to quote Martin Luther King Jr. to drive this home. “Darkness can’t drive out darkness. Only light can do that.”

This isn’t always the best match for a Democratic Party that’s enraged at Donald Trump. “I have these arguments on Twitter with supporters or fellow Democrats where they say, enough with the love and kindness stuff, Cory, we gotta fight,” Booker says. “When were those mutually exclusive?”

Booker has picked his fights, to be sure. In testifying against Jeff Sessions’s nomination as attorney general, he became the first sitting senator to testify against a fellow senator’s nomination for a Cabinet post. But the mood of the liberal base is warlike, particularly now that Trump appears wounded. Over the weekend, for instance, Booker faced pushback from some liberals for saying it was too early to talk about impeachment, and he wasn’t ready to join the Democratic National Committee’s call to revoke Jared Kushner’s security clearance.

But while Booker’s gentler approach frustrates Trump’s fiercer critics, it’s easy to imagine it appealing to voters who just want to move on from an ugly, conflictual era in American politics. Like Warren, Booker believes Trump fights for himself. But unlike Warren, he believes Democrats must show that politics doesn’t need to be a constant fight, that peace is possible.