(Sean Gallup/Getty Images)
Opinion writer

Barack Obama is worried:

“One of the things I do worry about sometimes among progressives in the United States — maybe it’s true here as well — is a certain kind of rigidity, where we say, ‘Oh, I’m sorry. This is how it’s going to be,’” Obama said.

He lamented that Democrats sometimes create “what’s called a ‘circular firing squad,’ where you start shooting at your allies because one of them is straying from purity on the issues.”

“When that happens, typically the overall effort and movement weakens. … You can’t set up a system in which you don’t compromise on anything. But you also can’t operate in a system where you compromise on everything; everything’s up for grabs. That requires a certain amount of internal reflection and deliberations,” he said.

Those remarks came at an event in Berlin, and while Obama wasn’t talking specifically about the 2020 presidential campaign, that’s what’s on everyone’s mind now. So it’s worth considering: Just what kind of risk do Democrats run if the candidates are subject to “purity tests”? Are they going to be weakened if they go after each other too much during the primaries? Will the eventual nominee emerge too wounded to beat President Trump?

On one hand, it’s not a surprise to hear Obama voicing these concerns, as someone both ideologically and temperamentally inclined toward compromise. On the other hand, as historian Julian Zelizer points out, if anyone should understand the value of a vigorous debate over issues in a primary campaign — and even a purity test or two — it’s Obama.

He became a viable candidate in 2008 in no small part because the party’s base was so disgusted with Democrats who voted for the Iraq War, including Hillary Clinton, Joe Biden, John Kerry, John Edwards, Charles E. Schumer, and Harry Reid. Obama, who had publicly opposed the war as a state senator in Illinois, was alone among the major candidates in being able to point to his opposition, satisfying a purity test that candidates such as Clinton and Edwards failed.

And that campaign was as hard-fought as nearly any in memory. When Obama won, there were some hard feelings to be soothed, but it didn’t stop the party from uniting around him.

You could tell a slightly different story about 2016, of course. But it’s hard to find cases in recent history where one of the two parties suffered because their party had been too strict about enforcing its beliefs. That’s not why Clinton lost, or Mitt Romney, or John McCain, or Kerry, or Al Gore. While many successful candidates claimed a desire to work across the aisle (Obama, Bill Clinton and George W. Bush all said they would), they didn’t win because voters had a burning desire for ideological moderation.

And while it’s true that many of the Democrats running for president are embracing policies that are further left than what they may have supported a few years ago, they’re doing what presidential candidates always do: responding to their party’s voters. And it happens that the things they’re advocating, such as universal health care, a higher minimum wage, marijuana legalization or stronger action on climate change, are pretty popular.

One must also remember that the Democratic Party is not one thing. It has a range of voices in it, and even if figures from the left such as Rep. Alexandria Ocasio-Cortez are more prominent than their counterparts might have been at an earlier time, they’re doing what they ought to do: push the boundaries, challenge the status quo and force new issues and perspectives into the debate. Then the party as a whole can hash them out, which is what happens in presidential primaries. The resulting agenda will be the product of that process and hopefully something the whole party can get behind.

It’s also important to remember that if you say that some particular thing — Medicare-for-all, for instance — shouldn’t be a litmus test, it’s not because you oppose litmus tests in general. Both parties have lots of them, and nobody has much of a problem with it. No Democrat can get their party’s nomination if they don’t defend a woman’s right to choose, progressive taxation, health care as a right — not a privilege — and strong protections for workers and the environment. Those are all litmus tests, as well they should be, because they define what it means to be a Democrat. Republicans have their own litmus tests on all those issues and more.

So when someone says “This shouldn’t be a litmus test,” the “this” is what matters — they’re saying that other positions should be litmus tests, just not this one. And that, too, is something Democrats and their candidates should debate. What principles can we absolutely not budge on, and where might there be some wiggle room? Some candidates more than others will have answers to those questions that the party’s voters find convincing.

So while no Democrat should want the candidates to get personally nasty, when it comes to issues, they should fire away at each other. This primary campaign is just getting going, but eventually it’s going to become passionate, maybe even a little angry now and again. That’s nothing for Democrats to fear.

Read more:

Kathleen Parker: The new litmus tests for future presidents could backfire against Democrats

Jennifer Rubin: Stacey Abrams gives a graduate school class on voter suppression

Carolyn Dupont: The left’s quest for purity could destroy potentially worthy leaders

E.J. Dionne Jr.: A bigger challenge to Democrats than socialists: Their liberal Republicans

Dana Milbank: Democrats are conspiring to reelect Trump

2020 Post Pundit Power Ranking: Joe Biden is getting dragged down by his own hands