Vivek Ramaswamy Won't Be Trump's Running Mate: Ex-President's Top Advisor

Donald Trump's top adviser has ruled out Vivek Ramaswamy as the ex-US president's running mate after the Republican frontrunner publicly criticised the Indian-American presidential candidate ahead of the Iowa caucus.

The Iowa caucuses, which begin on Monday, formally kick off the beginning of the long process by which the Republicans and Democrats choose their nominees for the presidential election on November 5.

Trump's top adviser, Jason Miller, told the New York Post that voters could "probably" rule out 38-year-old biotech entrepreneur Ramaswamy as the ex-president's running mate.

"Pretty safe to say it won't be Vivek," Miller was quoted as saying in the report.

On Saturday, Trump, 77, lashed out at Ramaswamy, who is most closely aligned with him in the race for the Republican nomination, accusing him of "deceitful campaign tricks".

The former president's criticism stemmed from shirts that Ramaswamy's campaign is handing out that say 'Save Trump, Vote Vivek' on them.

Ramaswamy posted a photo with a group of young men wearing them after his event in Rock Rapids, Iowa, on Saturday, which caught the former president's attention.

"Vivek started his campaign as a great supporter, 'the best President in generations,' etc. Unfortunately, now all he does is disguise his support in the form of deceitful campaign tricks," Trump wrote on Truth Social on Saturday.

"Very sly, but a vote for Vivek is a vote for the 'other side' - don't get duped by this. Vote for 'TRUMP, don't waste your vote! Vivek is not MAGA," he added.

The criticism marks the first time Trump and his team have made direct, public attacks against Ramaswamy.

Until now, Trump has largely avoided criticising Ramaswamy due to his strong praise and defence of the former president.

However, the criticisms come as voters will start making their voices heard in the first-in-the-nation caucuses on Monday and as Ramaswamy has started to become more direct in laying out the case for why he is the Trump alternative, ABC News said.

On the campaign trail, the biotech entrepreneur has pitched himself to Trump-leaning voters as the best of both worlds: someone with experience as a businessman who also has a deep understanding of the Constitution.

After Trump's post, Ramaswamy, who had previously stayed away from bashing Trump, again praised Trump.

Ramaswamy said he respects "the hell out of Trump" and that he's the "best President of the 21st century." According to the latest Des Moines Register/NBC News/Mediacom Iowa Poll, 48 per cent of likely Republican caucusgoers pick Trump as their first choice for president - a slight dip from the 51 per cent who said the same in December.

Nikki Haley, the Indian-American former US Ambassador to the UN and the lone woman in the party's presidential race has the support of 20 per cent support, an increase of four per cent, while Florida Governor Ron DeSantis slipped to third place with 16 per cent.

Though still in the race, Ramaswamy has now fallen back, and experts don't see much hope for the 38-year-old biotech entrepreneur during the primary season beginning on January 15. 

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)