Washington: Republican front-runner Donald Trump has regained the lead over rival Ted Cruz in Iowa, while Democratic front-runner Hillary Clinton is holding a three-point lead over Bernie Sanders, according to the final Des Moines Register/Bloomberg Politics before the Iowa caucuses.

Trump managed to earn the support of 28 percent of likely caucus-goers, while Cruz got 23 percent support, It was 15 percent for Florida Sen. Marco Rubio and 10 percent for former neurosurgeon Ben Carson.

On the Democratic, Clinton has the support of 45 voters, while Sanders is lagging behind at 42 percent, with just three percent for former Maryland Gov. Martin O'Malley.

The survey from pollster Ann Selzer was released just about 48 hours before voters will meet at the state's 1,681 precincts for Monday night's caucuses.

The Iowa poll is seen by many as a "gold standard" in the industry because it has a healthy record of predicting past contests with good accuracy. Selzer had foreseen Barack Obama's victory over Hillary Clinton in the 2008 caucuses, and she also forecast the late surge of Rick Santorum over Mitt Romney in 2012.

The poll conducted on January 26-29 has four percentage points margin error. The latest poll once again bring to fore the continuing slide for Cruz, who had grabbed a 10-point lead over Trump in the same poll in December. In early January, he led the billionaire businessman by three points.

Trump's supporters are seen as the most set in their choice, with 71 percent saying their mind is made up to support him on Monday. It is 61 percent for Cruz and 47 percent for Rubio.