The four candidates are billionaire real estate magnet Donald Trump; two first term Senators Ted Cruz from Texas and Marco Rubio from Florida and the Ohio Governor John Kasich.
Carson is also the first former presidential aspirant to be tapped by Trump in his Cabinet.
Former technology executive Carly Fiorina formally entered the 2016 United States presidential race on Monday.
Two-term Louisiana Governor Bobby Jindal, the first ever Indian-American to be elected as a state Governor, is among the shortlisted candidates for Trump's Cabinet, according to a media report.
Trump said he and his campaign has started to shortlist and compile "potential vice presidential" running mates which would include some of his former rivals in the Republican presidential primaries -- Ben Carson and Chris Christie.
Here are seven of the buzziest moments from the GOP's big night.
The debate over whether to allow Syrian refugees to settle in the United States took a dark twist after a leading presidential candidate likened those fleeing the violence in the Middle East to "rabid dogs".
In this moment there has to be honest acknowledgement of how so many in our community willingly voted for another four years of Trump, based on the morally flimsiest of reasons, points out Suleman Din.
Following their abysmal performance in the Iowa caucus and New Hampshire primary, New Jersey Governor Chris Christie and former corporate honcho Carly Fiorina have ended their campaigns to seek the Republican US presidential nomination.
President-elect Donald Trump has shaken up his White House transition team, appointing Vice President-elect Mike Pence as its head and three of his children as part of the group that would shape the direction of Trump's administration beginning January 2017
The names of two Indian-Americans -- Seema Verma and Bobby Jindal -- have emerged as possible candidates.
Facing no active opposition, Donald Trump on Wednesday cruised to victory in the Washington state primary and was just one step away from clinching the Republican presidential nomination to set up a likely clash with Hillary Clinton in the November polls.
Cruz only went as far as congratulating Trump, who was his bitter rival in the primary contests.
Terming China as "number-one abuser", leading Republican presidential candidate Donald Trump has alleged that the Communist nation, along with India, is taking advantage of the US through its economic policies.
The 69-year-old billionaire reality TV star has now won three of the four early nominating states, after convincing wins in South Carolina and New Hampshire.
Sikhs have been mistaken for terrorists and radicals and continue to suffer after 9/11 terror attacks in the US, community members feel following the latest attack on an elderly Sikh man in California which is being probed by police as a hate crime.
'I am in favour of keeping these talented people here so they can go to work in Silicon Valley.'
A total of 12 states from Alabama to Alaska are holding primaries or caucuses today. Virginia was the first state to open its polling stations at 6:00 am (16:30 IST).
Texas Senator Ted Cruz handed a shock defeat to controversial presidential contender Donald Trump in the Iowa Republican caucuses while in the Democratic camp both Hillary Clinton and Bernie Sanders claimed victories as the race for the White House began on Tuesday.
Democrat Hillary Clinton and Republican Donald Trump have both won the most states in the biggest day of the race for the US presidential nomination.
Bobby Jindal's tirade against Donald Trump -- like his performance in the polls -- hardly got any traction
Incoming US President Donald Trump has assembled a core team that is -- not surprisingly -- overwhelmingly white and male.
'We don't have to be the world's policeman. We don't have to impose our values. But we need to lead and when we pull back as we've done, you begin to see exactly what happens -- the voids are filled by threats of terror that countries have to suffer with, including India.'