By Chris Kahn
NEW YORK (Reuters) - A majority of Americans say Democrat Hillary Clinton won Monday night's presidential debate, but her performance doesn't appear to have immediately boosted her support among likely voters, according to a Reuters/Ipsos national tracking poll released on Wednesday.
The online poll, which gathered responses from more than 2,000 people on Tuesday, found 56 percent of American adults felt that Clinton did a better job than Trump in the first of their three televised debates, compared with 26 percent who felt that Trump did better.
Of those who thought Clinton emerged the victor, 85 percent were Democrats and 22 percent were Republicans.
U.S. presidential debates have historically been seen as a crucial test of candidates' poise and policies. Monday's was watched by a record 84 million viewers and was billed as a rare prime-time opportunity for two unpopular candidates to convince millions of undecided voters to back them.
Afterward, both candidates claimed victory.
"“Every single online poll had me winning,” Trump said at a campaign stop in Council Bluffs, Iowa on Wednesday. "You sit back and you hear how well she did in the debate. I don’t think she did well at all.”
Clinton campaign spokesman Jesse Ferguson said the Democrat clearly won the debate as Trump "was unprepared, became unhinged and was incoherent throughout."
Among those who are expected to take part in the Nov. 8 general election, 34 percent said they felt that the debate changed their view of Clinton in a positive way, compared with 19 percent who said the same of Trump.
Some 31 percent of likely voters said the debate improved Clinton's chances of winning the White House, while 16 percent said the debate benefited Trump.
Even so, Clinton's performance seemed to have little impact on her support among America's likely voters. The poll showed 42 percent supported Clinton while 38 percent supported Trump. Over the past few weeks Clinton has maintained a lead of between 4 and 6 points over Trump.
Narrowing the focus to likely voters who watched the debate, Clinton led Trump 44 percent to 39 percent.
One possible reason for the lack of movement in her support is that it usually takes several days to measure the full impact of a single event, like a debate, said Donald Green, a political scientist at Columbia University.
The Reuters/Ipsos poll is conducted every day in English in all 50 states. Monday's sample of 2,036 American adults included 1,336 people who were considered to be likely voters from their voting record, registration status and stated intention to vote in the election. Among those likely voters, 1,026 said they watched some portion of the debate on live TV, online or in media clips that were circulated after the debate.
The poll has a credibility interval, a measure of accuracy, of 3 percentage points for the entire sample and the sample of likely voters. It has a credibility interval of 4 percentage points for the likely voters who watched the debate.
National opinion polls have differed this year in how they measure support for Clinton and Trump. Some polls, like Reuters/Ipsos, try to include only likely voters, while others include all registered voters. The Reuters/Ipsos tracking poll gathers responses every day and reports results twice a week, so it often detects trends in sentiment before most other polls.
Polling aggregators, which calculate averages of major polls, have shown that Clinton's lead over Trump has been shrinking this month to about 2 percentage points.
(Reporting by Chris Kahn, editing by Richard Valdmanis and Ross Colvin)