WASHINGTON — There could be a war with Iran. There's already a trade war with China. Venezuela is in crisis. North Korea is not giving up nukes. And Russia is up to its usual tricks.

But you won't hear much about any of that on the Democratic presidential campaign trail. And while most of the leading candidates touch on foreign policy on their campaign websites, it's often only in short and broad statements that lay out universal principals like keeping Americans safe, while offering little in the way of details.

And some party leaders say that has to change since national security is always one catastrophe away from being the only issue anyone cares about, and Washington these days seems perpetually on the brink of crisis.

"I'm just surprised nobody's talking about it because this is where Donald Trump is weakest," presidential contender Rep. Seth Moulton, D-Mass., told NBC News last week, the day after a confrontation with Rep. Liz Cheney, R-Wyo., on Iran.

"This is the most reckless commander-in-chief perhaps in American history, and we can't just ignore that," Moulton said.

A largely unknown Marine combat veteran, Moulton has positioned himself as the national security expert in the crowded Democratic field.

It's a spot no one else seems to want it, at least so far.

With a near daily rollout of detailed policy statements and legislation, the Democrat have churned through everything from slavery reparations to abolishing the Senate's legislative filibuster to saving the planet from climate change — but they have barely skimmed the world and America's place in it.

That's a stark contrast to the last time Democrats had a sprawling presidential primary — in 2008, when the Iraq War was the biggest issue and the main one separating the two final candidates, Barack Obama and Hillary Clinton, though it took a back seat in the 2016 contest between Clinton and Sen. Bernie Sanders, I-Vt.

Sen. Chris Murphy, D-Conn., has warned that Democrats need to do more to close "the national security gap" with Republicans, who Americans have viewed for decades as better able to defend the country from attack.

"I think it is going to be a key element of Trump's strategy in 2020," Murphy said last week at a conference organized by National Security Action, a new group of former Obama administration officials. "If we don't actively talk about our plans to protect the country ... then we will not close that gap.”

But among Democratic primary voters, there's little interest.

A recent NBC News/Wall Street Journal poll found just 11 percent of respondents said national security and terrorism should be the top priority of the federal government, down from 21 percent at a similar point in the last presidential election cycle. And those questions rarely get put to candidates by voters as they visit the early voting states around the country.

"It's hard to get people to care about foreign policy, generally," said Tommy Vietor, a former Obama national security spokesperson who now hosts Pod Save the World, a foreign policy spinoff of the popular Pod Save America podcast.

But he predicted candidates won't be able to avoid the issues forever and noted that foreign policy is the one place where presidents can implement their vision without worrying too much about Congress or the courts.

"It's surprising to me how much time candidates spend debating policy that they may never end up getting through Congress when, on foreign policy, as president, you have full latitude to act on your own," he said.

One reason is that few of the Democratic presidential candidates have much experience in international relations and may feel more comfortable sticking to familiar domestic turf, especially when voters aren't demanding it.

It used to be accepted as fact that no one could win the White House without passing the "commander-in-chief test," which meant projecting strength, a steady hand and expertise on national security, but recent elections have scrambled the rules of American politics.

Clinton twice tried and failed to exploit the test. First, in 2008 against Obama, her campaign produced an ad asking voters if they wanted Obama, an inexperienced freshman senator from Illinois, answering a 3 a.m. phone call about a global crisis. Then, Clinton and her allies tried in 2016 when they borrowed the mushroom cloud page from Lyndon Johnson's playbook to question Trump's temperament.

In both cases, her successful opponents countered that they had better judgment on world affairs, even if she had more experience.

Stephen Miles, the director of Win Without War, a progressive national security coalition, said Trump was effective in 2016 by painting Democrats as defenders of a creaky foreign policy establishment that had led to endless wars, controversial trade deals and pointless foreign aggression.

In 2020, he said, candidates should offer an alternative not only to Trump, but also to the old way of doing things. "Trying to defend the failed status quo is not going to fly, so what is your take?” he said.

But he pointed to some candidates who have started to take steps to do that, even if it's far from being the centerpieces of their campaigns.

Sanders has given some speeches on foreign policy, hired a well-known adviser and pushed congressional resolutions against the Trump administration’s policy toward the Yemeni civil war.

Sen. Elizabeth Warren, D-Mass., who joined the Senate Armed Services Committee a few years ago in part to bolster her limited foreign policy experience, recently has become more active on that panel and laid out her vision in a speech and article in Foreign Affairs.

And while many Democrats may not agree with her worldview, longshot contender Rep. Tulsi Gabbard, D-Hawaii, a military veteran, has made foreign policy central to her presidential bid.

But the candidate with by far the most experience in that realm is former Vice President Joe Biden. When speaking, he weaves in stories about world leaders and mockery of Trump's warmth to North Korean leader Kim Jong Un.

"I know all the world leaders," Biden said in an interview with a South Carolina NBC affiliate. "I'm the guy that told the Chinese that when they set up these air defense zones, we're going to fly right through them."

Jesse Lehrich, a foreign policy spokesperson on Clinton's 2016 campaign, summed it up: "I get it — Democratic primary voters aren't clamoring for detailed plans on countering terrorism in the Sahel. But there's a real opportunity to put forward an affirmative vision of American leadership."

CORRECTION: (May 20, 2019, 8:47 a.m. ET): An earlier version of this article misquoted former Vice President Joe Biden. He said, "I'm the guy that told the Chinese that when they set up these air defense zones, we're going to fly right through them." Biden did not say "when they set up these air defense bombers, we're going to fly right through them."