Hillary Clinton has two problems she needs to solve. If she wins the Democratic primary, she needs to do so without alienating Bernie Sanders's voters. And if she's going to win the general election and govern effectively afterward, she needs to run a campaign that doesn't completely alienate independents and Republicans.
Both problems may have the same solution: Donald J. Trump.
Up until a few weeks ago, the Clinton campaign didn't really believe they could be so lucky as to have Trump as the Republican nominee. Marco Rubio has long been the candidate they feared most among Republicans, and the smart money was still that he would win the GOP primary.
Clinton's team thought they could beat Rubio, but it was going to be ugly — he's a young, likable guy, and they'd have to tear him down to win.
But now it looks like Trump might really secure the Republican nomination. And that makes Clinton's job a lot easier.
Democrats are likely to unify no matter whom the Republicans choose, but Trump is loathed by the left in a way the other Republicans simply aren't. A February Economist/YouGov poll found that while 43 percent of Democrats had a "very unfavorable" opinion of Marco Rubio, 71 percent of Democrats had a very unfavorable opinion of Donald Trump.
Trump, however, isn't simply loathed among Democrats. He's also disliked by independents, and he's controversial even among Republicans. Forty-two percent of independents, and 24 percent of Republicans, have a very unfavorable view of Trump. The numbers for Rubio are 24 percent and 9 percent, respectively.
And it's not just polls. Elite Republicans are already starting to say that they'll vote for Clinton over Trump — a phenomenon that will likely be small, but will serve to signal how broad opposition to Trump really is.
Making Clinton's job even easier is that Trump's message is itself divisive — it's soaked in racial resentment and xenophobia, and delivered through insults and angry rants. It's also, crucially, understood by mediating institutions like the press to be a divisive message. Trump's candidacy is (correctly) covered as an unusually ugly, rage-powered phenomenon.
It's worth noting here that Clinton also has very high unfavorables. She is about as divisive a figure as exists in the normal realm of American politics, but Trump is something new, and he has cut through the Republican Party by exploiting tensions most politicians fear to inflame.
Trump sets up Clinton for a much softer and unifying message than she'd be able to get away with against a candidate like Rubio, and you could see her previewing it in her South Carolina victory speech.
"Despite what you hear," Clinton said, "we don't need to make America great again. America has never stopped being great. But we do need to make America whole again. Instead of building walls, we need to be tearing down barriers."
Trump may be the only force in American politics able to make Clinton into a uniter and not a divider.
Clinton's people have their hands full winning the Democratic primary. But if they had a vote in the Republican primary right now, they would be casting it for Trump.