American military aid to Israel is shaping up to be a wedge issue in the 2020 presidential election.

Three major contenders for the Democratic Party nomination - Pete Buttigieg, Bernie Sanders and Elizabeth Warren - now subscribe to a position that U.S. military assistance should not be used in service of West Bank annexation.

Sanders has even suggested immediate aid cuts, with some American funding redirected for humanitarian purposes to the Gaza Strip.

At the other end of the Democratic primary field, former Vice President Joe Biden has categorically ruled out conditioning aid to Israel, condemning the very idea as "absolutely outrageous."

Behind these seemingly firm stances, the candidates’ positions on aid actually raise more questions about the future of the U.S.-Israel relationship than they answer.

Open gallery view Democratic presidential candidates Mayor Pete Buttigieg, left, Sen. Elizabeth Warren and Sen. Bernie Sanders. Credit: Evan Agostini, AP / Darron Cummings, AP / John Locher, AP

Despite all this newfound willingness to relate to the idea of conditioning aid, American military assistance is unlikely to be the first item on the chopping block should the next U.S. administration see Israel cross a red line on annexation.

That is because conditioning the security aid Washington provides Israel would be the single most politically fraught way for a Democratic White House to counter annexation. It could effectively require the U.S. to sign off on Israel’s operational use of U.S.-subsidized military equipment, to ensure it was not being used for blacklisted purposes.

But that money is fungible. Israel may use ultimately purchase the same or similar kinds equipment for critical national security purposes - purposes no Democratic presidential nominee would oppose - to protect its borders with hostile neighbors in Syria, Lebanon, and Gaza, and to manage real security threats that may emanate from the West Bank - but also to police Palestinians in the occupied territories.

If the next Democratic president seeks to somehow scale back or condition American military aid to Israel, they may face legal hurdles as well.

In recent months, both Congress and the Senate have advanced legislation that would in effect codify the $3.3 billion in foreign military financing allotted annually to Israel under the current bilateral memorandum of understanding as a minimum for future aid packages. Neither bill has made it through the other house, but they could prove relevant down the line.

The approach floated by Buttigieg, Sanders, and Warren, entailing either deducting the expenses of annexation from future assistance, or ensuring U.S. aid is not used in annexed territory, is bound to be more complicated than campaign trail soundbites would suggest.

There’s an additional factor, largely outside the candidates’ control: No one can possibly predict what the Israeli government’s makeup or objectives will look like in January 2021. So both conditioning aid, and Biden’s rejection of that path, cannot be understood as ironclad commitments. There are simply too many variables to account for.

If anything, a future Democratic administration’s first approach is likely to be a rollback of the political freebies President Donald Trump gave to the Israeli government during his time in office.

Trump has fulfilled a number of items on the Israeli right’s wishlist: recognition of Jerusalem as Israel’s capital, relocation of the American Embassy there, shuttering the PLO mission in Washington, and completely cutting off funding for UNRWA as well as for USAID operations in the West Bank and Gaza Strip.

Open gallery view Israel's Prime Minister Benjamin Netanyahu delivers his speech as U.S. ambassador to Israel David Friedman listen, during the opening ceremony of the new U.S. embassy in Jerusalem, May 14, 2018. Credit: Sebastian Scheiner/AP

But each of these "gifts" can be taken away or reversed with relative ease. In this sense, Trump has actually laid very clear foundations for a future American policy of pressure against Israel, while the Democratic candidates’ positions on military aid remain in flux.

If the next president revokes the Trump administration’s program of hyper-supportive policies towards Israel’s right-wing government, and hostility towards Palestinians, they will not simply be returning American foreign policy to its pre-2017 orientation.

Thanks to partisan agitation by Trump and Netanyahu, U.S. policies that once received bipartisan backing – like funding for UNRWA and support for USAID programs in the Palestinian Territories such as support for schools and hospitals – are now perceived in certain quarters as being pro-Palestinian and even anti-Israel. Any rollback of Trump’s agenda will therefore create the appearance of a divide between the United States and Israel.

In fact, a future president may deliberately leverage a return to what was a previous status quo in an attempt to alter Israeli behavior – without touching military aid.

In some cases, Trump’s policies will not simply be undone. Trump’s actions have moved the goal posts in both directions, meaning that both future Democratic and Republican policies toward Israel and the Palestinians are bound to be further apart than they were before 2017.

For instance, the Democratic analog to Trump moving the U.S. embassy to Jerusalem would not necessarily mean returning it to Tel Aviv, and reopening the relatively autonomous U.S. Consulate in East Jerusalem. A new policy could see a full-fledged embassy to the Palestinian Authority - or perhaps to a State of Palestine, if America confers unilateral recognition.

Even though these policies are likely to precede a decision on the all-important question of American military aid, they may not be the only instruments of pressure a Democratic administration brings to bear against Israel.

Whatever the complications inherent in executing the policies that Buttigieg, Sanders, and Warren support, there is no discounting the fact that if there is political will, there may be a way.

Open gallery view Supporters of the Likud party and its leader, Israeli Prime Minister Benjamin Netanyahu, raise Trump 2020 banners as they await results of the elections in Tel Aviv, Israel. Sept. 17, 2019 Credit: Ariel Schalit,AP

Benjamin Netanyahu’s eventual exit from politics could ease tensions with Democrats, but 2020 primary talk of conditioning aid has shifted expectations with left-wing voters. It will be difficult, if not impossible, to put the genie back in the bottle - regardless of who holds the premiership in Israel, and who wins the Democratic nomination.

The best Israel can do in this context is to not give the United States a reason to resort to these kinds of measures. But that is scant reason to be optimistic.

The Democratic candidates who have waded into the aid issue have tied freezing or reducing security assistance to annexation, even though Israel has long undertaken steps to de facto cement its control in the West Bank. That means a politically savvy Israeli leader may simply be willing to toe the line with the United States while creeping annexation proceeds apace.

On the other hand, a significant contingent of Knesset members present and future see the project of Greater Israel as their raison d’etre. Many in Netanyahu’s Likud party, including his rival Gideon Saar, came out explicitly in favor of annexation long before the prime minister did.

In a nod to Netanyahu’s Iran deal opposition, these individuals may someday find it politically advantageous to stage a confrontation with the United States, demonstrating their diplomatic "courage" by "standing up" to a U.S. administration perceived as unfriendly.

Indeed, the more ideological segments of the Israeli right will not so readily abandon their pro-annexation convictions, even if it means setting Israel on a collision course with the next American president, placing critical security assistance and the broader U.S.-Israel relationship at risk.

Evan Gottesman is the Associate Director of Policy and Communications at Israel Policy Forum. Twitter: @EvanGottesman