Donald Trump and Ted Cruz
Donald Trump (left) has overtaken Ted Cruz in the influential Iowa caucus, according to a recent poll Reuters

Donald Trump and Ted Cruz have no chance of winning a US general election with the voters of America, a senior election strategist who is campaigning for Hillary Clinton, has claimed. Jim Messina said his Republican Party rivals had "gone off the rails."

Messina, who was Barack Obama's campaign manager in 2012 said Donald Trump upset voters "every time he opens his mouth."

"I just saw a statistic that 47% of Americans are very opposed to Donald Trump's candidacy," he told Sky News. "That's not a winning recipe in a general election."

He said that the Republican Party were in "uncharted territory" adding that "every single day they seem to make my day by saying crazier and crazier things."

Messina, who is campaigning for the Democrat Party's frontrunner for the presidential nomination, Hillary Clinton, added that neither Donald Trump nor Ted Cruz "has any chance of winning a general election with the voters of America."

Trump recently stunned his Republican running mates by failing to attend 28 January's final presidential debate before the influential Iowa caucus – the first nomination contest of the 2016 election season.

In doing so, he cast a shadow over his rivals as no one appeared to emerge as a central challenger to him during the two-hour face-off in Iowa's state capital, Des Moines.

The former reality TV star held a competing event across town that he said raised $6m (£4.2m) for U.S. military veterans.

Iowa helps shape the race to the White House by being the first state to hold a caucus deciding each party's nominee. On the Republican side, voters listen to speeches before casting their vote in a secret ballot. The votes are tallied across the state and winner is subsequently declared.

The process is less straightforward on the Democrats side. The number of people in the room are counted, and any candidate who does not get a certain percentage (a threshold set at the beginning of the night) in the first round, is eliminated.

Those who voted for losing candidates are then coaxed by the others to join their side and to vote for their candidate of choice. At the end, the results are collated across the state in all precincts.

Despite the emphasis placed the Iowa caucuses, the real impact of this process happens further down the line, when results are eventually translated into votes for delegates, who represent their states at their respective party conventions. These delegates are the ones who vote for a candidate to run in the national election.

The Iowa poll will take place across 1,744 precincts across Iowa and will be held in churches, libraries and other smaller venues on 1 February. In one of the final polls before the Iowa caucus "the Donald" has surged past Ted Cruz, while Clinton is holding a three-point lead over her main rival Bernie Sanders.

Trump captures the support of 28% of likely caucus-goers, compared to 23% for Cruz, according the poll taken to The Des Moines Register newspaper and Bloomberg Politics.

The Iowa poll is widely viewed as one of the best in the industry because of its record of accurately predicting past contests. The survey from highly respected pollster Ann Selzer foresaw Barack Obama's victory over Hillary Clinton in the 2008 caucuses, and Rick Santorum's late surge over Mitt Romney in 2012.

The poll was conducted January 26-29, and the margin of error is four percentage points.