Indian-American presidential hopefuls Nikki Haley and Vivek Ramaswamy are among the four candidates who have qualified for the fourth Republican primary debate scheduled to take place in Alabama on Wednesday, the smallest debate stage lineup so far this year.

The Republican Party's third presidential debate took place in Miami, Florida, on November 8.

Florida Governor Ron DeSantis, former New Jersey Gov. Chris Christie, two-term former South Carolina Governor Nikki Haley and biotech entrepreneur Vivek Ramaswamy will participate in the fourth primary debate of the 2024 election cycle, the Republican National Committee (RNC) announced on Monday.

The four candidates, comprising the smallest debate stage lineup so far this year, will face off at the University of Alabama in Tuscaloosa, CBS News reported.

Former President Donald Trump, who continues to be the most popular leader in the Republican Party with an approval rating of over 60 per cent, is not expected to participate in the debate. Trump has skipped all previous debates as well.

The announcement comes with just six weeks to go until the Iowa caucuses open the 2024 Republican nomination calendar, and as DeSantis and Haley compete fiercely to be seen as the top primary rival to Trump, CNN reported.

Haley, the only woman on the GOP primary debate stage, received a big boost towards her presidential ambition in November as she landed an endorsement from powerful conservative money bags Koch brother-backed American for Prosperity network.

The 51-year-old former US Ambassador to the UN got the endorsement by the influential Americans for Prosperity super-PAC, which said it is endorsing Haley for president and added that she is best positioned to beat Trump in the primary elections and incumbent President Joe Biden, a Democrat, in the 2024 presidential elections in November 2024.

Ramaswamy, the multimillionaire biotech entrepreneur, has been trailing Trump and several other 2024 Republican contenders in early state polls.

The 38-year-old launched his campaign in February as a little-known candidate, later emerging in the summer as a breakout star. But Ramaswamy struggled to keep up that momentum.

The other Republican presidential candidates have targeted Ramaswamy during those debates over his lack of political experience and on several controversial foreign policy stances about US involvement in Taiwan and Israel.

Haley and Ramaswamy have clashed publicly during the last two of the three Republican primary debates.

The threshold set by the RNC to qualify for the fourth debate was the highest set so far, demanding that candidates reach at least six per cent support in two national polls or 6 per cent in one national poll as well as two polls from four of the early-voting states — Iowa, New Hampshire, Nevada and South Carolina, the report said.

The RNC approved the polls that would qualify candidates. Candidates also needed a minimum of 80,000 unique donors, with at least 200 from 20 states or territories.

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