(CNN)Donald Trump would be wise to watch Guatemala's run-off presidential election this weekend closely.
On Sunday, voters will return to the polls to decide between former Guatemalan first lady Sandra Torres and Alejandro Giammattei, a former head of the country's prison system. And it's an election that's proven to be nothing short of fascinating for many reasons.
The winner will lead not only Central America's most populous country, but also the nation which has become the leading source of migrants traveling to the US-Mexico border.
This means Guatemala's next president may find themselves on the receiving end of immense pressure from the US president and his administration. Limiting the number of migrants making it to the United States has been the centerpiece of Trump's policy agenda.
Guatemala's next president will be tasked with overseeing the final implementation of a controversial agreement reached between Trump and his Guatemalan counterpart, outgoing President Jimmy Morales, in late July. The deal has not yet been ratified by Guatemala.
Labeled as a "safe third agreement" by the White House, the deal would commit Guatemala to extending asylum to migrants who seek it when moving through the country. It would also make some asylum-seekers who pass through Guatemala ineligible for protection in the US. (Read the deal itself here.)
Critics say the preliminary arrangement endangers asylum seekers and may violate a court ruling stipulating that Morales cannot enter any "safe third" agreement without congressional approval.
When pressed Thursday on a time frame for the deal's implementation, US Customs and Border Patrol (CBP) commissioner Mark Morgan said: "We're still waiting on the government of Guatemala to ratify that. We're hoping anytime."<