(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."
Just days before the deal was signed, Trump appeared to threaten Guatemala, saying: "We're looking at something very severe with respect to Guatemala."
This, along with other disparaging statements from Trump directed at the Guatemalan government, could be a sign that the biggest critic of the incoming administration may be nearly 3,000 miles away in Washington.
Former first lady vs. the "Eternal Candidate"
Both candidates for the Guatemalan presidency met with acting Homeland Security Secretary Kevin McAleenan last week to discuss the deal, according to the Washington Post. McAleenan has been visiting Guatemala in recent months as the two countries sought to reach an asylum agreement.
Torres and Giammattei have each questioned Morales' authority to sign the deal in the first place, with Torres, 63, tweeting the hashtag "NoAl3erPaisSeguro" (No to Safe Third Country).
"We ask President Morales to abstain from signing that agreement because we do not have many resources for our own people, much less can we keep foreigners here and give them attention," she wrote.
Torres, from the center-left Unidad Nacional de Esperanza party (UNE), won 25% of the first vote in early June, nearly double the votes of her second-round rival. If elected, she would become the country's first female president -- but she brings political baggage with her.
Between 2008 and 2012, she served as Guatemala's first lady during the presidency of her husband, Alvaro Colom. She often acted beyond the remit of her ceremonial duties by assuming control of many of the country's social programs, says Marielos Chang, political scientist at the Universidad Francisco Marroquin in Guatemala City. She also attracted criticism due to a lack of transparency over funding.