WASHINGTON • The spotlight has rarely found Dr Ben Carson in recent months.

While other presidential candidates shot flaming arrows at rivals and, sometimes, the news media, the soft-spoken Dr Carson seemed to struggle to be noticed.

"Well, thank you," he told moderators in the first Republican debate. "I wasn't sure if I would get to speak again."

But while almost all Republicans were upstaged by the bombast of Mr Donald Trump in recent months, Dr Carson, a retired neurosurgeon whose low-key personality and celebrated medical career are the antithesis of a politician's usual path, gained ground as few seemed to notice.

A recent Quinnipiac University national poll showed him in second place in the Republican field, and a Monmouth University survey of Iowa Republicans released on Monday had him tied with Mr Trump. Another Iowa poll, by The Des Moines Register and Bloomberg, had the two candidates running closely within the poll's margin of sampling error.

The polls came as CNN changed its rules for the next Republican presidential debate in a way that could give former business executive Carly Fiorina a chance to take the stage with the main contenders for the party's 2016 presidential nomination.

The cable network, which is sponsoring the Sept 16 debate, said on Tuesday that any candidate who ranks in the top 10 in polling since the first debate on Aug 6 would be included in the next prime-time debate.

CNN originally had planned to include poll results dating to July 16 to determine the participants, but Ms Fiorina criticised that plan because it would not have taken into account her surge in support since the first debate.

Ms Fiorina was widely viewed as the winner of the "undercard" debate of low-polling candidates that took place hours before the higher-ranking rivals competed in Cleveland. "I really look forward to the debate," Ms Fiorina said after the announcement.

Dr Carson also cheered CNN's decision and urged the network to go further, expanding the prime-time debate to include all Republican candidates.

Dr Carson, like Mr Trump and Ms Fiorina, has never held elected office, a quality that seems particularly prized by Republican voters this year. More than 90 per cent of voters in the Register/Bloomberg poll conducted last week said they were unsatisfied with the government and politicians.

And yet, in almost every other way, Dr Carson is Mr Trump's opposite. He is almost professorial, where Mr Trump is loud, combative and unfiltered.

"At the end of the day, I attribute it to the power of nice," said Mr Rob Taylor, chairman of Dr Carson's campaign in Iowa, reflecting on the rise of his candidate.

Dr Carson has worked hard to tame his habit of making highly provocative statements, often on homosexuality, a move that advisers said had saved his campaign after it nearly derailed amid early headlines.

A little-known figure to most voters before the first Republican debate in Cleveland on Aug 6, Dr Carson clearly benefited from the huge number of viewers who tuned in because of Mr Trump's flamboyance. Dr Carson spoke of separating conjoined twins and removing half a brain as qualifications for the Oval Office in his closing statement - made off the cuff, his advisers say. Many commentators shrugged, but social media lit up. Polling before and after the debate showed Dr Carson with one of the biggest upticks.

The money for television ads and a campaign organisation beyond the first nominating states will be a challenge for Dr Carson. Although he raised a respectable US$10.6 million (S$15 million) through the first half of the year, most of it was from small donors who are costly to solicit through e-mails and direct mail.

Dr Carson has already burned through more than half the money he has raised.

NEW YORK TIMES, REUTERS