Presidential hopeful Jeb Bush’s biggest donor has published an attack letter in newspapers in Miami, Las Vegas and Des Moines urging voters to rally against Donald Trump.

Mike Fernandez, who has contributed over $3m to Bush’s campaign, issued the ads in response to a recent CNN poll in which Trump seized 36 per cent of the Republican vote.

In an emotion-driven tirade Fernandez lashed at Trump’s controversial immigration policies: “I write as an immigrant, exiled from the tyranny of a dictatorship. I have served this country in our armed forces. I love this beacon of freedom and land of opportunity… surely, we are better people than to agree with this man’s sound bites and raucous rallies and think the worst in us is right for this country?”

“Our nation deserves thoughtful candidates with inspiration and ideas that speak to the best in all of us.”

Fernandez concluded: “See the "hater" for what he is – an insecure, narcissistic BULLYionaire with a hunger to be adored.”

Read the full ad here.