There was something touching and elegant in the images of Rashida Tlaib — the working-class daughter of a Ford assembly line worker — being sworn in as a member of the new House of Representative earlier this month wearing a traditional Palestinian thobe.

In a hand-embroidered gown, stitched by her mother, the first Palestinian-American woman to make it to Washington cut an impressive figure.

And then the video of her vowing to supporters “we’re gonna impeach the motherf****r” went viral.

It’s quite an achievement to allow Donald Trump to clamber onto the moral high ground when it comes to the subject of personal abuse, but, somehow, Ms Tlaib contrived to pull it off.

“I think President Trump has met his match,” she nonchalantly boasted afterwards.

While many on the left cheered Ms Tlaib’s defiance, even some of the president’s critics warned against the “Trumpification” of political discourse, arguing that she was simply mirroring Mr Trump’s debasement of American civic life.

That same contemptuous attitude towards political norms was on display elsewhere this month but this time with a rather darker undertone.

As the Senate considered a measure to empower state and local governments that want to counter the BDS movement, Ms Tlaib tweeted: “They forgot what country they represent. This is the U.S. where boycotting is a right & part of our historical fight for freedom & equality. Maybe a refresher on our U.S. Constitution is in order, then get back to opening up our government instead of taking our rights away.” Ms Tlaib immediately came under fire from Abe Foxman, the former national director of the Anti-Defamation League, who accused her of engaging in a “classic antisemitic canard of double loyalty”.

Ms Tlaib’s fellow Democrats didn’t pull their punches, either. “We oppose your charge of dual loyalty,” the Jewish Democratic Council of America tweeted. “It’s wrong, dangerous and hurts the cause of peace.”

Once again, Ms Tlaib refused to retreat, responding to criticism from the bill’s sponsor, Republican senator Marco Rubio, by arguing: “It’s clear my earlier tweet was critical of US Senators like yourself, who are seeking to strip Americans of their constitutional right to free speech.”

There were sound reasons to oppose Senate Republicans’ attempt to turn support for Israel into a political football as a way of distracting attention from Mr Trump’s unpopular shutdown of the federal government.

Even Democrats such as Senator Ben Cardin, who has pushed anti-BDS legislation, oppose the Republicans’ tactics, while other moderate, pro-Israel Democrats, such as Senator Dianne Feinstein, say they cannot support legislation which they believe restricts First Amendment rights to free speech.

Foreign policy commentator Josh Rogin has argued the Republicans are attempting to set a trap for aspiring Democrat presidential candidates.

Referring to growing anti-Israel sentiment among left-wing grassroots Democrats who will help pick the party’s 2020 nominee, he suggested: “Each of the dozen or more Democratic lawmakers potentially running for president will have to take a position [on the anti-BDS bill], one that either hurts them with progressives in the primary or moderates in the general election.”

For Republicans, Ms Tlaib is proving the perfect foil; the face of the anti-Israel far-left which it wants to claim now dominates the Democratic Party. In truth, Ms Tlaib’s support for BDS and a one-state solution is not shared by leaders of the party’s left-wing, such as Senator Bernie Sanders. Her about-turn — she had previously indicated support for two states — led the liberal, pro-Israel lobby group J Street to take the unprecedented step of rescinding its endorsement of her prior to last November’s elections.

Thus came the warning from Matt Lewis — a conservative pundit who is a Trump critic — that Ms Tlaib is in danger of becoming “the Michele Bachmann of the left”.

Ms Bachmann, a hard-right favourite of the Tea Party, briefly shot to fame for her base-pleasing, moderate-repelling rhetoric in the early years of Barack Obama’s presidency.

It is all a far cry from last summer, when Politico magazine lauded 42-year-old Ms Tlaib as “the left’s way forward”, describing her as “steady”, “savvy” and “more poised and knowledgeable” than the likes of rising Democrat star Alexandria Ocasio-Cortez, with whom she is often compared.

It cited her solid record as a state legislator representing an urban Detroit district and her equally impressive electoral history.

Those who believe the Palestinian cause needs more moderate, eloquent voices in Washington may conclude that Ms Tlaib does not yet seem ready to fulfil that role.