Meg Whitman, chief executive of Hewlett-Packard, has thrown her support behind Hillary Clinton. (Drew Angerer/Getty Images)

Meg Whitman, the Silicon Valley executive and prolific Republican fundraiser, endorsed Hillary Clinton for president last night.

In a Facebook post, she said Donald Trump’s “unsteady hand would endanger our prosperity and national security. His authoritarian character could threaten much more.”

Whitman’s views on Trump are no surprise. The unsuccessful Republican candidate for governor of California in 2010 compared him to Adolf Hitler and Benito Mussolini at a June meeting in Utah of Republican donors and executives and helped bankroll an anti-Trump super PAC in the spring. She is close to 2012 Republican nominee Mitt Romney, the sponsor of that meeting, where she also reportedly indicated that she would probably be supporting Clinton.

But few, if any, Republicans as prominent and financially potent as Whitman have gone so far to defect to Trump’s Democratic opponent, whom she praised for her experience and “stable and aspirational leadership.”

Whitman is the chief executive of Hewlett-Packard Enterprise and former CEO of eBay.

Here’s what she wrote:

As a proud Republican, casting my vote for President has usually been a simple matter. This year is different. To vote Republican out of party loyalty alone would be to endorse a candidacy that I believe has exploited anger, grievance, xenophobia and racial division. Donald Trump’s demagoguery has undermined the fabric of our national character.

Trump’s reckless and uninformed positions on critical issues — from immigration to our economy and foreign policy — have made it abundantly clear that he lacks both the policy depth and sound judgment required as President. Trump’s unsteady hand would endanger our prosperity and national security. His authoritarian character could threaten much more.

Therefore, I have decided to support Hillary Rodham Clinton. It is clear to me that Secretary Clinton’s temperament, global experience and commitment to America’s bedrock national values would make her the far better choice in 2016 for President of the United States. In a tumultuous world, America needs the kind of stable and aspirational leadership Secretary Clinton can provide. I urge all Republicans to reject Donald Trump this November.

In an interview with the New York Times, Whitman added: “I will vote for Hillary, I will talk to my Republican friends about helping her, and I will donate to her campaign and try to raise money for her.” The Times said Clinton phoned Whitman about a month ago.

She told the Times she stood by her Hitler and Mussolini comparison: “‘Time and again history has shown that when demagogues have gotten power or come close to getting power, it usually does not end well.’”

Whitman was a supporter of Chris Christie before he dropped out of the Republican primary race and endorsed Trump, an action that she denounced as “an astonishing display of political opportunism.” She urged Christie donors to “reject the governor and Donald Trump outright. … For some of us, principle and country still matter.”

Whitman lost California’s 2010 gubernatorial race to Democrat Jerry Brown, despite spending $140 million of her own money on the race.