For a man who claims his deal-making abilities are second to no one, it was the ultimate trade-off.

Donald Trump, in return for a huge down-payment on his signature campaign pledge to build a wall along the Mexican border, was to sign a congressional bill backed by moderate Republicans and Democrats to protect the so-called “dreamers” — immigrants brought illegally into the US by their parents when they were children.

That deal — one the President had repeatedly signalled he was willing to strike — now lies in tatters after ferocious White House attacks effectively sank a bipartisan immigration plan when the Senate voted on it earlier this month. 

The finger of blame for the defeat has been pointed squarely at Stephen Miller, an immigration hardliner and the President’s most influential domestic policy adviser.

It deprived Mr Trump of a much-needed win in Congress, with the mid-term elections barely eight months away. 

It also left 700,000 undocumented young immigrants facing the threat of deportation when President Obama’s Deferred Action for Childhood Arrivals programme — scrapped by Mr Trump last September — officially expires on March 5.

Mr Miller is said to have strengthened Mr Trump’s right-wing sinews — and recruited anti-immigration Republicans to scupper the effort — when the President originally appeared close to backing a bipartisan reform bill in January.

Senator Lindsey Graham, a senior Republican senator and leading player in the push to broker a compromise, suggested he “is an outlier on immigration, he’s an extremist and the President — who had turned the keys of the car over to him — will never get anywhere.”

Mr Miller, who hails from a Democrat-voting Jewish home in California, was a close ally of Steve Bannon, the President’s far-right former chief strategy adviser. The pair worked together on both Mr Trump’s controversial inauguration address and the Muslim travel ban, which the President tried to implement shortly after coming into office.

Mr Bannon’s departure from the White House last summer was seen at the time as a victory for those who wished to steer Mr Trump towards a more moderate, conventional agenda. 

However, as the Washington Post suggested, the defeat of the bipartisan Senate immigration bill suggests that “the ideologues are ascendant”. Chief among them is Mr Miller, who has effectively replaced Mr Bannon as the President’s chief political strategist and keeper of the Trump campaign’s nationalist conscience.

Working with Democrats to provide an “amnesty” for illegal immigrants, Mr Miller believes, was never supposed to be part of Mr Trump’s agenda.

This ideological zeal puts him at odds with the other senior Jewish members of the administration. The President’s daughter Ivanka and son-in-law, Jared Kushner, have long been seen as having more liberal sympathies.

Donald Trump’s top economic adviser, Gary Cohn, treasury secretary Steve Mnuchin and Mr Kushner are all former donors to the Democrats. Mr Cohn, who voted for Hillary Clinton, remains a registered Democrat.

Mr Miller is also an outlier when it comes to the wider US Jewish community. 

Hardline rhetoric on immigration in Mr Trump’s State of the Union address last month sparked criticism from B’nai B’rith, the Anti-Defamation League and the Hebrew Immigration Aid Society.

Earlier this month, 17 Jewish groups — among them J Street — called for Mr Miller to be sacked, accusing him of “extreme viewpoints and advocacy of racist policies”.

“As Jews, we are in solidarity with immigrants and refugees and believe that our nation must be a refuge and welcoming home for new Americans,” they wrote. 

Not that such attacks are likely to worry Mr Miller. As he well knows, his boss in the Oval Office regards them as a badge of honour.