22 liberal groups have united behind a campaign to stop the 69-year-old real estate magnate with a plan that includes anti-Trump demonstrations, possibly including protests at the Republican National Convention this summer in Cleveland, and marches in major cities.
"Donald Trump's candidacy is a threat to the America we love, and we must respond to him and what he is stoking as such - with a nonviolent movement grounded in love and community that ensures that he never comes anywhere near the White House, and perhaps even more importantly, makes clear to every other politician and every person in the United States that racist demagoguery is a dead-end political strategy that most Americans reject," the groups said in an open joint letter.
"We are calling for a massive nonviolent mobilisation of working people, students, immigrants, children of immigrants, great-great-grandchildren of immigrants, people of colour and white people, the unemployed and under-employed, people of faith, retirees, veterans, women, and men - anyone who opposes bigotry and hate and loves freedom and justice - to stand up to Trump's bullying and bigotry," the letter said.
"So far, Trump has bounced around the country speaking to people in these stadium rallies, and we haven't seen massive marches outside the rallies," Ben Wikler, Washington director for Moveon.Org, said.
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The Trump Campaign, however, asserted that such a move would backfire, citing the fate of Republican candidates who had attacked Trump.
"What you find with Donald Trump is he's a counter- puncher. Someone punches him and he punches back, and he punches back much harder. That's what the Republican field has come to realise," Corey Lewandowski, the Trump campaign manager, said.
Top Republican leadership, its backers and its major fund
raisers yesterday ganged up against the party's presidential front-runner Trump - who has suddenly caught the imagination of the party's mass base in less than nine months of joining politics - with the sole objective of preventing him to be its presidential nominee.
After the last Tuesday's primary, wherein he won in three States and is leading in another where official results are yet to be declared, Trump has best chance to get the Republican nomination as he is way ahead of his other two rivals - Senator Ted Cruz and Ohio Governor John Kasich - in delegate count.
With 673 delegates, Trump needs to win about half of the rest of delegates in contention, Cruz needs to bag 80 per cent of them and Kasich has an impossible target of 114 percent of the total delegates yet to be won.
"He (Trump) shouldn't be president of the United States," Quin Hillyer, a conservative columnist told reporters after the meeting of some two dozens of these leaders.
"Not only is he not conservative, he's also just not a good face for the country," said Hillyer, spokesman of the group.
"We encourage all former Republican candidates not currently supporting Trump to unite against him and encourage all candidates to hold their delegates on the first ballot," the group said in a statement, as there was indication that Cruz is now the new poster boy for the establishment.
The Senator was once a vocal opponent of Cruz.
"The consensus was that we need a unity ticket of some sort and we'll let the candidates work out who the unity ticket is," Hillyer said after the meeting.
"Obviously, more conservatives seem to prefer Cruz to Kasich, and Cruz has more delegates right now, so if you do the math, it's probably more likely to be Cruz-Kasich," he said.
Meanwhile, writing for The Washington Post, eminent columnist Fareed Zakaria said having described Trump as an unacceptable, unconservative, dangerous demagogue, the party establishment appears to be making its peace with the man who keeps winning primaries.