Washington (AFP) - President Donald Trump's decision to recognize Jerusalem as Israel's capital has reverberated across the Middle East and the world, but the motives for his move may lie in politics at home.
In fulfilling an explosive campaign promise, Trump has prompted rioting in Ramallah, put the already moribund Middle East peace process in doubt and cleaved a wedge between the United States and its allies.
Yet crucially for this embattled US president, he has also shored up his evangelical Christian base, squared away further support from a vital donor and burnished his image as a political iconoclast.
Presidents Bill Clinton and George W. Bush had made the same promise to move the US embassy to Jerusalem, but faced with the same destabilizing consequences, backed down.
Trump's political brand is to show no such queasiness.
"It's a fetish, and I'm convinced Trump is driven in part by a desire to make his predecessors look bad by comparison," said Larry Sabato of the University of Virginia. "'They ignored their promises. I fulfilled mine.'"
- Familiar playbook -
Trump's announcement in the Diplomatic Reception Room of the White House carried more than a hint of deja vu.
Two months ago, in the same room, before the same podium, beneath the same emblematic portrait of America's founding father George Washington, Trump launched a similar foreign policy gambit.
Then, he shocked allies by questioning a deal to curb Iran's nuclear program. On Wednesday it was picking sides in the blood feud over control of Jerusalem.
During the Great Recession and World War II, Franklin Roosevelt used the Diplomatic Reception Room for his "fireside chats," designed to sooth and reassure an anxious nation.
Trump has twice in his young presidency used the room to light a match that risked setting the Middle East ablaze.
But on both Iran and Jerusalem, aides say Trump made it crystal clear early on that he was determined to fulfil his pledge to voters.
He baulked at the timidity of advisors -- like Secretary of State Rex Tillerson and Pentagon chief James Mattis -- who warned of grim consequences, according to people familiar with the discussions.
At a November 27 meeting of the National Security Council on Jerusalem, Trump gave more weight to the voices of UN ambassador Nikki Haley and Vice President Mike Pence.
"The Vice President argued that this is our moment to take decisive action," one White House aide told AFP. "The president was very receptive to that."
Pence and Haley's deep interest and involvement in that decision was not a coincidence.
- Religious right -
Pence, who late last month courted pro-Israel groups in New York, has also been one of the links between the administration and mega donor Sheldon Adelson.
The casino magnate threw tens of millions of dollars behind Trump's presidential campaign and has lobbied vociferously for the White House to recognize Jerusalem.
And since being selected as Trump's running mate in July 2016, Pence has been an even more crucial bridge between the bombastic New Yorker and those evangelical voters that helped propel him to the White House.
Both he and Haley are strong advocates for a religious right that has given Jerusalem policy surprising weight.
Around 76 percent of evangelical voters aged over 65 -- a group that voted overwhelmingly for Trump -- have a positive view of Israel, according to a survey by LifeWay.
And a significant portion of evangelicals believe that regaining control of Jerusalem's Temple Mount would set in motion events in the Book of Revelation, according to author and religious scholar Diana Butler Bass.
Trump does not share that view, but facing a battle for the soul of the Republican Party, midterm elections in 2018 that could see Democrats make significant gains and a Russia investigation that threatens his presidency, he must keep diehard supporters onside.
During Wednesday's announcement, Trump and Pence stood side-by-side, both wearing blue ties and white shirts that echoed the Israeli flag, offering a small hint at the motive behind a move that echoes far beyond the United States.