The two men — both in their 30s, both trusted aides of older, familial leaders — struck a bond. As their countries' chief negotiators on Israeli-Palestinian peace, Kushner and the Saudi prince were both looking to make a name for themselves on the world stage and consulted with each other frequently over the following months.
Kushner championed Crown Prince Mohammed to the president and senior foreign policy officials, some of whom expressed wariness at the embrace of MBS, as he is known in diplomatic circles.
The two men's relationship also played a key role in Riyadh becoming the unlikely first stop on Trump's maiden international trip in May 2017. Trump, despite endorsing a travel ban on Muslims during his campaign, became the first U.S. president to make his official first trip to an Islamic nation.
Relations between the two countries are complex because they are entwined on energy, military, economic and intelligence issues. The Trump administration has aggressively courted the Saudis for support of its Middle East agenda to counter Iranian influence, fight extremism and forge peace between Israel and the Palestinians.
"We want to have a relationship with Saudi Arabia. They're a strategic partner. They're a mortal enemy of the Iranians. They're helping us on terrorism," said Sen. Lindsey Graham, R-S.C., a Trump supporter and top member of the Senate Foreign Relations Committee.
"Having said all that, if this did happen — and it's increasingly likely that something bad happened to this man at the hands of the Saudi government — that shows contempt for us. That's disrespectful to us. It puts people like me in a box who've been one of the leading champions of the relationship."
It's not just Graham who's in a box. It's also Trump, who has long-standing business ties to Saudi Arabia.
Jeff Prescott, who was senior director for the Middle East at the National Security Council during the Obama administration, said that a reassessment of the U.S. relationship with Saudi Arabia is overdue and that Trump should raise U.S. complaints with Saudi leaders.
"What the Trump administration has given Saudi Arabia is a green light to pursue any policy," said Prescott, now executive director of National Security Action, a group of former officials opposed to the Trump administration. "The key question is whether Republicans will have the courage to force the administration to have a reckoning of the relationship."
He said Kushner's project to forge peace between Israel and the Palestinians also could be in jeopardy.
"There is no question that a rift with Saudi Arabia — or even relations strained by pressure from Congress — would make an already bleak prospect even less likely," Prescott said.
In Congress, there is a push for sanctions under a human rights law, and lawmakers are questioning American support for the Saudi-led bombing campaign against Iranian-backed rebels in Yemen. The U.S. has raised concerns previously about heavy civilian casualties caused by the Saudi-led coalition fighting in Yemen.
Sen. Chris Murphy, D-Conn., voiced doubt there would be support in Congress for another arms sale to Saudi Arabia — though lawmakers haven't blocked sales before. He also called for at least a temporary halt in U.S. military support for the Saudi bombing campaign in Yemen. Murphy tweeted that if Saudi Arabia is found complicit in Khashoggi's death, it should be viewed as a "fundamental break in our relationship with Saudi Arabia."