REUTERS/Rick Wilking
On Saturday evening, The Des Moines Register/Bloomberg Politics survey found Trump leading Sen. Ted Cruz (R-Texas) 28% to 23% among likely GOP caucus-goers.
The poll, conducted by veteran pollster J. Ann Selzer, also found Sen. Marco Rubio (R-Florida) with 15% and retired neurosurgeon Ben Carson at 10%.
"Trump is leading with both the inner core of the caucus universe and the fringe - that's what any candidate would want," Selzer said.
Earlier this month, Selzer's poll found Cruz with a three-point lead in Iowa, while the majority of other polls have found Trump ahead there. Iowa will be the first state to weigh in on the presidential primary next Monday and both Trump and Cruz have aggressively competed to win its caucus.
On the Democratic side of the race, former Secretary of State Hillary Clinton led her chief rival, Sen. Bernie Sanders (I-Vermont), 45% to 43%.
Selzer's poll is widely respected in the political world. In a profile this week, the statistical news website FiveThirtyEight called Selzer "the best pollster in politics." The Register noted that her poll is known as the "gold standard" due to its historical accuracy. A Politico profile last December further described her as "legendary."
Here's Politico's account of Selzer's final polls before recent elections:
The recent track record of her firm, Selzer & Company, is impressive: Selzer, who has polled for the Des Moines Register for decades, was the only pollster to nail the order of Democratic candidates in 2004. Her final poll before the 2008 caucuses accurately predicted that a surge of first-time caucusgoers would propel Barack Obama to a decisive victory. Selzer saw former Pennsylvania Sen. Rick Santorum's surge in the waning days before the 2012 GOP caucuses when few others did.
And just last year, the final Register poll in the Iowa Senate race showed Republican Joni Ernst with a 7-point lead, contrary to other polls that showed a much closer race with Democrat Bruce Braley. Braley's campaign decried the poll, calling it an "outlier." But Ernst won by 9 points.