A survey asking Republican supporters in the key US state of Iowa to pick a presidential candidate has placed Texas Senator Ted Cruz ahead of Donald Trump, who leads in most national polls.
The poll, ordered by Bloomberg Politics and The Des Moines Register, gave Mr Cruz a 10-point lead over Mr Trump.
Iowa helps shape the race to the White House by being the first state to hold a caucus deciding each party's nominee.
The latest survey suggests a higher chance of a bitter, protracted primary.
According to the New York Times, the arch-conservative Mr Cruz could emerge as the preferred nominee of far-right Republicans, competing against Mr Trump - cast as an anti-establishment candidate - and against a possible third candidate representing the centre-right of the party.
Both Mr Cruz and Mr Trump have been campaigning heavily in Iowa, and hope victory in the 1 February caucus will galvanise their race for the Republican nomination.
In the poll, 31% of respondents wanted Mr Cruz to secure the nomination, compared with 21% naming Mr Trump as their first choice ( BBC )
