Pulling no punches in San Diego last night (2 June), Clinton questioned Trump's credentials on foreign policy, diplomacy and the economy while raising alarm at the prospect of the Republican presumptive nominee becoming commander-in-chief of the US.
"Donald Trump's ideas aren't just different, they're dangerously incoherent. They're not even really ideas, just a series of bizarre rants, personal feuds and outright lies," she said, as she sought to effectively disqualify him as a credible candidate.
"He is not just unprepared. He is temperamentally unfit to hold an office that requires knowledge, stability and immense responsibility," she added. And Clinton did not stop in her evisceration of Trump there, but went on to warn of catastrophic security consequences for the US if Trump won the White House.
"He should not have the nuclear codes because it's very easy to imagine Donald Trump leading us into a war just because someone got under his very thin skin," said Clinton. "We cannot let him roll the dice with America."
She continued: "Imagine Donald Trump sitting in the situation room making life or death decisions on behalf of the United States. Do we want him making those calls? Someone thin-skinned and quick to anger. Do we want his finger anywhere near the button? Making Donald Trump our commander-in-chief would be a historic mistake."
Earlier this week, Clinton said she is in talks with Democratic rival Bernie Sanders' campaign to unite the party and "prevent Donald Trump from getting anywhere near the White House." Her speech last night was significant in that it was the first signal of the type of fierce tactics she will use to dissuade voters from backing Trump if she manages to edge Sanders out for the party nomination. Clinton is just 70 delegates shy of clinching victory to set up a head-to-head with the billionaire businessman.
She also blasted Trump's praise for authoritarian leaders, including Russia's Vladimir Putin and North Korea's Kim Jong-Un. "I will leave it to the psychiatrists to explain his affection for tyrants ... If Donald gets his way they'll be celebrating in the Kremlin. We cannot let that happen," she said.
The former first lady added: "He says he has foreign policy experience because he ran the Miss Universe pageant in Russia."
At one point, Clinton also remarked that Trump was likely preparing a barrage of tweets in response to her criticisms – and they soon followed.
"Bad performance by Crooked Hillary Clinton! Reading poorly from the telepromter [sic]! She doesn't even look presidential!" tweeted Trump.
But a fiery Clinton was in no mood to field criticisms from Trump, and responded: "Imagine if he had not just his Twitter account at his disposal when he's angry, but America's entire arsenal."