President Trump is on the cusp of being impeached for asking Ukraine to investigate 2016 election meddling — and possibly Hunter Biden’s work with a natural gas company — as a precondition for receiving U.S. foreign aid.

This, Democrats say, is a classic case of a “quid pro quo” (the Latin term for “this for that”).

Whatever one thinks about the case against Trump, it’s worth asking: Is a quid pro quo automatically scandalous?

After all, Democrats’ leading 2020 candidates have repeatedly pledged to use exactly this technique to advance their own political interests.

Last night during a Weather Channel special on global warming, Sen. Cory Booker (D-N.J.) said he would tell foreign nations that aid is “contingent” on adopting U.S. climate policies.

“This is not just rejoining the Paris Climate Accords, which I will do right away, it’s actually using every lever of foreign policy we have for more foreign aid to countries, making a contingent on climate action,” Booker said. “It means using our diplomacy, our alliances, our trade deals, centered to that must be labor and climate.”

Mayor Pete Buttigieg has repeatedly said he would withhold aid to Israel until the country agrees to stop building new settlements in disputed territories.

Sen. Elizabeth Warren (D-Mass.) said aid would be “on the table” if Israel doesn’t halt settlement construction.

Sen. Bernie Sanders (I-Vt.) said he would “absolutely” use aid to Israel as leverage to push through policy change within Israel.

Rep. Julian Castro (D-Texas) said he would, too — although not as a first resort.

“You would not necessarily want to leverage U.S. aid to Israel to push him to do that, is what you’re saying?” CNN’s Jake Tapper asked.

“Well, that would not be my first move,” Castro replied, but added: I’m not saying that would never happen.”

And that’s just a sampling. For more, check out the supercut above.

(Watch on YouTube)