New Jersey Governor Chris Christie and gormer business executive Carly Fiorina have both announced they are ending their campaigns for the 2016 Republican presidential nomination.
Mr Christie has pulled out of the race after a poor showing in the New Hampshire primary yesterday, narrowing the field of rivals facing businessman Donald Trump for the right to compete in the 8 November US presidential election has narrowed.
His sixth-place finish in the New Hampshire primary raised doubts about his viability as a candidate.
In a post on his Facebook page, Mr Christie said he was leaving the race "without an ounce of regret".
Fellow Republican Ms Fiorina, a former Hewlett Packard chief executive, said in a Facebook post she would suspend her campaign.
Mr Trump's remaining opponents, most of them mainstream Republicans, will likely benefit from their departures, which leaves seven Republicans from a field that once had 17 candidates.
Mr Christie had poured much of his campaign's resources into New Hampshire and had considered a good showing there critical.
He won only around 7% percent of votes yesterday, despite a good performance at a Republican debate last weekend.
Mr Trump and Democrat Bernie Sanders coasted to victory on a wave of voter anger in the New Hampshire presidential nominating contest, thrashing traditional US politicians in a display of anti-establishment power.
New Hampshire's verdict sets up a tough fight for Republicans in South Carolina's 20 February primary and for Democrats there on 27 February.
Some of the most monumental campaign battles in elections past have been fought in the state that holds the first primary election of the American South.
Ohio Governor John Kasich won a spirited fight for second in the Republican field in New Hampshire, with Senator Ted Cruz of Texas, former Florida Governor Jeb Bush and Senator Marco Rubio of Florida fighting for third place.
All four are now headed to South Carolina.
For Mr Trump, New Hampshire showed he has staying power and can take a punch after losing on 1 February to Mr Cruz in the first nominating contest, the Iowa caucuses.
His win showed pundits were wrong to think he would quickly self-destruct based on his penchant for insults and imprecise plans for the presidency.
Former US Secretary of State Hillary Clinton, now looks wounded, trailing Mr Sanders by 60% to 39% based on 86% of the returns.
She barely won Iowa and now has been trounced in New Hampshire, where young voters liked Mr Sanders' populist proposals to break up big banks and have the government pay for free college tuition.
"People have every right to be angry but they're also hungry, they're hungry for solutions," Mrs Clinton said after congratulating Mr Sanders.
"I will work harder than anyone to actually make the changes that make your lives better."
She was headed to New York, headquarters for her campaign, to regroup with top aides and prepare for a Democratic debate tomorrow.
Her campaign has denied reports it is considering a shakeup but acknowledged it would be natural to add members to their team as the campaign progresses.
Mr Sanders said his victory showed "we have sent the message that will echo from Wall Street to Washington, from Maine to California, and that is that the government of our great country belongs to all of the people and not just a handful of wealthy campaign contributors."
Some 73% of voters say they think the United States is on the wrong track and these disaffected people make up a majority of the support bases for Mr Trump and Mr Sanders, according to a Reuters/Ipsos poll.
They are worried about the economy and distrust establishment politicians they perceive as being part of the problem.
Mr Trump who has campaigned to deport illegal immigrants and temporarily ban Muslims from entering the United States, was in first place with 35% of the vote on the Republican side based on 88% of returns.
At his victory rally, Mr Trump congratulated other candidates in the race but promised to soon return to his pugnacious approach.
"Tomorrow: boom, boom," he said, shadow boxing while his supporters cheered.
The New Hampshire Republican race confirmed that Mr Trump is being helped by the lack of a strong establishment contender against him.