What the top Democrats are offering the world

If a Democrat wins back the White House in 2020, they'll face steep obstacles to turning their domestic agenda into reality.

But, but, but: In foreign affairs, particularly when crises arise, they will wield immense power.

There's a week left before Iowa, and Joe Biden, Bernie Sanders and Elizabeth Warren — easily the top three candidates in national polls — have recently produced a flurry of recent writing and rhetoric on foreign policy.

• I took a close look, and these are my key takeaways:

Biden's foreign policy centers around restoring America's global leadership and alliances.

• He argues that will allow him to repair global institutions, defend the international rules of the road, confront China — which he increasingly cites as a priority — and rein in Russia.
• Biden sounds more prepared to support foreign intervention and free trade deals than his leading rivals, though less than some Democrats (including himself) in cycles past.
• Key policies: Biden wants a cautious withdrawal from Afghanistan, more military aid to Ukraine and sanctions on those responsible for China's mass detentions in Xinjiang.
• Between the lines: His pitch boils down to, essentially, everything you liked about Obama's foreign policy and less of what you didn't.

Sanders is more likely to condemn American imperialism than launch into Biden-style celebrations of American greatness — though he also emphasizes re-establishing U.S. moral authority.

• Sanders has made common cause with leftists around the world for decades, sometimes controversially.
• But his foreign policy platform is not as radical as some might imagine. He supports U.S. membership in NATO (though, like Trump, he wants allies to foot more of the bill) and won't rule out using military force (though he sets a high bar).
• Key policies: Sanders wants to scale back the U.S. drone program, drastically cut the military budget and increase foreign aid. He hates most proposed trade deals, including the Obama-era Trans-Pacific Partnership and Trump's NAFTA replacement (which Warren backed).

Warren contends that America has hurt itself and the world by promoting globalization, big corporations and a model of capitalism that drives inequality and resentment.

• She's skeptical of the IMF, wants to break up "multinational monopolies" and "crack down on tax havens."
• Warren plans to slash the Pentagon's budget and increase the State Department's. Like Sanders, Warren frames many U.S. interventions as harmful to the countries concerned and the Americans funding them.
• Key policies: Warren says she'd need a clear national security imperative and congressional approval to use military force. She has ruled out "first use" of a nuclear weapon and vowed not to appoint donors as ambassadors.

Between the lines: Warren and Sanders have similar diagnoses in terms of the failures of U.S. foreign policy, and many of the same prescriptions.

• Sanders places more emphasis on righting historical wrongs and on the global struggle against injustice and "oligarchy."
• Warren, meanwhile, says America needs to renew itself at home first if it hopes to lead abroad.

Common ground:

• All three want to return to the Paris Climate Accord and spur international action on climate change.
• They all support a two-state solution in the Middle East and think the U.S.-Saudi partnership must be scaled back.