The UN migration agency elects a new director general on Friday in a vote that will test US influence in a major international organisation, with Washington's candidate battling accusations of bigotry against Muslims.
The head of the International Organization for Migration (IOM) has been an American throughout the agency's 67-year history with one exception from 1961 to 1969.
But President Donald Trump's nominee Ken Isaacs, a longstanding executive with the Christian charity Samaritan's Purse, has faced unprecedented challenges.
Trump's hardline stance on migration -- from the so-called Muslim ban to his "zero tolerance" policy on the southern US border that led to separating parents and children -- has complicated Washington's traditional right to choose the world's top migration official.
Trump's "America First" administration has also levelled ferocious attacks against multilateral bodies including last week's decision to quit the UN Human Rights Council, which rankled diplomats in Geneva where IOM is also based.
But Trump aside, the damage to Isaacs's candidacy has mostly been self-inflicted.
Isaacs, who also worked for the United States development agency (USAID) during George W. Bush's presidency, has published numerous tweets describing Islam as an inherently violent religion, including one after the 2016 attacks in the French city of Nice that said "Islam is not peaceful".
He has also retweeted xenophobic anti-Islam material, like a post last year from Robert Spencer, the director of Jihad Watch, which argued "peaceful Muslims" and "Jihadis" were indistinguishable.
Isaacs made his Twitter account private amid the uproar that followed his nomination in February.
But he has not denied responsibility for his inflammatory comments and has apologised for any offence caused.
He told AFP in March that his decades-long record of humanitarian work, especially in majority Muslim countries like Bangladesh, Iraq and Sudan proves he is not a bigot.
He also insisted that he had convinced IOM member states that he held no religious prejudices.
But for some, like the head of the NGO Refugees International Eric Schwartz, Isaacs's past comments are disqualifying, despite his respected humanitarian record.
"Imagine, for instance, had a candidate for this position made a similar succession of disparaging remarks about Jews, Catholics, evangelical Christians or any other religious group," Schwartz wrote in an op-ed in Monday's Washington Post.
"Would anyone seriously suggest that such statements should not present a bar from assuming such an important office as director general of IOM?", added Schwartz, who served as an assistant secretary of state under former US president Barack Obama.
It is unclear how the vote will go as Isaacs is facing two challengers for the post: current IOM deputy chief Laura Thompson of Costa Rica and Portuguese politician Antonio Vitorino, a former EU commissioner.
Voting among IOM's 172 member-states is by secret ballot and candidates need a two-thirds majority to win.
On another key issue, Isaacs has not unequivocally recognised the science establishing the causal link between human activity and climate change.
"I am not a climatologist, I am not going to jump into that discussion at all," he said in March.
He does however recognise that environmental factors like drought and floods are increasingly forcing people to migrate and said he would have no problem implementing IOM's already established "action objectives" on climate change.
Isaacs is vying to replace veteran US diplomat William Lacy Swing, who held senior State Department and UN posts over a career spanning half a century.
Swing has not said whether he thinks Isaacs is right for the job.
But when asked last month about the climate science denial issue in particular, Swing said: "It is important to recognise basic facts and realities."
Expertise on migration, he added, is not a prerequisite.
"I knew virtually zero about migration," when elected in 2008. "I've had to learn on the job."
Swing also pointed out that the job has changed dramatically over the past decade.
In 2008, conversations about migration "didn't last very long" because few were interested, whereas the subject has now become a urgent political priority in nearly every IOM member state, Swing told reporters in Geneva.