Many seasoned politicians roll their eyes at such questions. “I don’t go to moral victory speeches,” Rahm Emanuel recently told an audience in California. “It’s about winning, because if you win you then have the power to go do what has to get done.” But left unsaid is what, exactly, needs to get done—or why. Hillary Clinton had plenty of detailed policy ideas, but the bigger principles or goals often went missing. Just saying “stronger together” didn’t cut it.

Democrats also have to decide if they want to wage all-out war against Trump. The Democratic base all over the country is pressuring legislators to pursue a campaign of blanket resistance to the White House: whatever Trump wants, just vote no. The idea mirrors the tactics of Senator Mitch McConnell, who famously announced, “The single most important thing we want to achieve is for President Obama to be a one-term president.” Since Republicans gained seats in Congress, McConnell’s approach seemed to be vindicated. Just do the same to the current president, many Democrats suggest, and win that way.

But there are serious limits to what such an approach accomplishes. Republicans have the majority, and they’re using it. Democrats have put up symbolic fights of “No,” but Trump’s Cabinet appointees are getting confirmed. Democrats will try to make life hard for Supreme Court nominee Neil Gorsuch, something that honor almost demands after what Republicans did to stonewall Barack Obama’s nominee Merrick Garland. But they can’t stop him.

George Bush erased our budget surplus, presided over 9/11, and invaded Iraq. The response of voters: let’s have another round!

More important are the costs of stubborn resistance. When Republicans refused to get involved in health-care reform, Obama wound up having to negotiate exclusively with his own side, throwing in special sweeteners and baking in flaws that might have been excised had Republicans tried in good faith to improve the bill. Not only did Republican intransigence fail to stop Obamacare, it also ensured that Republicans would hate the result even more.

Republican obstructionism didn’t help Republicans with their presidential campaigns, either. Precisely when the G.O.P. needed to remake itself and recover from the Bush years, it instead became a party frozen in place. Instead of re-examining its values and looking for ways to cooperate across party lines, it concentrated solely on tactics. That’s one reason that Mitt Romney offered voters nothing more than Bushism, but with better looks. It was doomed to fail. Had Marco Rubio, who offered Bushism with updated donor-class accessories, gone up against Clinton in 2016, he would probably would have done no better, and he certainly wouldn’t have flipped Rust Belt states like Michigan or Wisconsin, both of which Trump won.

There’s also one important difference between the policy divisions of today and yesteryear. Obama offered cross-party cooperation but not realignment. His policy priorities and outlook were those of his party alone, and he was not fighting his own side. Since McConnell never cared about healthcare reform, getting in the way of it was painless. By contrast, if Obama had come out of the gate pushing for huge tax cuts, Republicans would have had a much harder time saying no. That’s where Trump is a little different. He cares about the Republican Party only as a means by which to enact his agenda, and he’s willing to defy it when it pleases his base. If he passes an infrastructure bill with help from Democrats, Trump is happy. The same goes for a bill with tariffs on imports. That makes the case for blanket resistance weaker. To be sure, if this is war—if the only goal is to defeat Trump—then you might hurt yourself to hurt Trump, just as you might bomb your own bridges if it prevents the advance of your enemy. But that’s taking things even further than Republicans did with Obama, and it’s sacrificing a lot for the cause.

Finally, Democrats have to decide whom they’re going to run in 2020. That’s mighty tough. Already, we’re hearing arguments suggesting that Hillary Clinton could somehow be back. But she won’t be. At least not once voters have weighed in. As for the other possibilities, few are ideal. Tim Kaine is seasoned, but he will have trouble filling a stadium—or a living room. Elizabeth Warren will be 71 in 2020, and to see her more is to like her less. Bernie Sanders will be 79. Cory Booker is a show horse who isn’t that beloved in his home state. So it won’t be easy. Likelier to emerge are governors with names like Hickenlooper (first name John) or lesser-known Rust Belt types like Sherrod Brown (although he will be 68). Or maybe Al Gore, who’ll be 72. Is it finally time?