By James Oliphant

WASHINGTON (Reuters) - After a week in which he hosted Saturday Night Live and stood center-stage at a Republican debate, Donald Trump is surging among Republicans likely to cast votes in the party’s presidential primary.

According to the five-day rolling Reuters/Ipsos presidential poll, Trump has leapt some 17 percentage points among likely Republican voters since Nov. 6, when he was essentially tied with Ben Carson at about 25 percent. Trump now captures 42 percent of those voters while Carson has fallen off slightly.

Among all Republicans - not simply likely primary voters -Trump holds a substantial edge over Carson, at 34 percent to about 20 percent, according to the Reuters/Ipsos poll.

Trump’s appearance on NBC's Saturday Night Live earned the program its highest ratings in two years, with 9.3 million viewers tuning in. Then, on Tuesday, 13.5 million viewers watched the debate from Milwaukee broadcast on the Fox Business Network.

It remains to be seen, however, whether Trump’s surge will hold in the wake of his comments at an Iowa rally Thursday night in which he tore into Carson, telling the crowd that Carson has a "pathological" temper.

"If you’re pathological, there’s no cure for that,” Trump said. "If you’re a child molester, there’s no cure for that.”

Trump then posted a video critical of Carson on his Instagram account Friday.

The Republican establishment has long expected the outspoken billionaire to fade, and he has yet to give it the satisfaction. Trump has consistently held more than 25 percent of the support among all Republicans in the Reuters/Ipsos rolling poll for more than two months.

The Reuters/Ipsos poll is also bad news for Marco Rubio, who is widely considered to be emerging as the establishment-backed alternative to Trump. Despite receiving rave notices for his past two debate performance, Rubio’s support has remained flat, with about 10 percent of likely Republican primary voters preferring him.

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Those primary voters remain very down on former Florida Gov. Jeb Bush. Just four percent say they would support Bush in the latest poll.

The results of the five-day rolling Reuters/Ipsos poll was based on a sample of 534 Republicans with a credibility interval of 5 percent. The pool of likely Republican primary voters was based on sample of 257 voters with a credibility interval of 7 percent.

(Reporting by James Oliphant; Editing by Chizu Nomiyama)