"I am proud to endorse Donald J Trump for President of the United States of America," Palin, a Tea Party icon, told a cheering crowd of Trump supporters at a rally in Iowa yesterday.

Her support is the highest-profile backing for Trump so far.

It came the same day that Iowa's Republican governor, Terry Branstad, said he hoped that Texas Senator Ted Cruz would be defeated in Iowa. The February 1 caucuses are a must-win for the Texas senator, who is running neck-and-neck with Trump in state polls. Trump said he is proud to receive Palin's endorsement.

Palin served as the Governor of Alaska before being selected as Senator John McCain's Vice Presidential nominee in 2008.

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