Hillary Clinton delivered a blistering rebuke of Donald Trump's foreign policy agenda Thursday, warning he is “temperamentally unfit” to hold the job of commander in chief and would destabilize national security with his “bizarre rants, personal feuds and outright lies.”

The address in San Diego was Clinton's most aggressive broadside against Trump yet, and it offered a preview of the lines of attack and tone the Democratic front-runner is likely to take as the race moves past the primary and into the general election.

On a stage packed with American flags and before an audience that included military personnel, Clinton presented voters with what her campaign feels confident will be a sobering and provocative question: Whose finger do they want on the nuclear button?

Clinton is capitalizing on Trump's struggle to explain multiple contradictions and gaps in the foreign policy vision he has laid out. Trump has yet to offer a comprehensive strategy for confronting the most pressing national security concerns. He has made several remarks seemingly on the fly, such as proposing that Japan be armed with nuclear weapons. Sometimes, Trump has later retracted such comments, as he did this week in the case of the nuclear weapons remark.

Clinton contrasted Trump's plans to her own as “not just different, they are dangerously incoherent. They are not even really ideas, just a series of bizarre rants, personal feuds and outright lies.”

Trump's immediate response came by tweet. “Bad performance by Crooked Hillary Clinton!” he wrote. “Reading poorly from the telepromter!(sic) She doesn't even look presidential!” He also tweeted: “Crooked Hillary no longer has credibility — too much failure in office.”

Clinton anticipated the taunts, remarking in the speech: “We all know the tools Donald Trump brings to the table: bragging, mocking, composing nasty tweets. I'm willing to bet he is writing a few right now.”

Clinton turned her fire toward Trump even as she is still consumed with her primary battle in California against Vermont Sen. Bernie Sanders, whose aggressive campaigning in the state has enabled him to erase most of the lead Clinton long enjoyed. Although Sanders was not mentioned by name, the speech was designed, in part, to help persuade wavering voters not to cast ballots for him.

It built off the case Gov. Jerry Brown of California made when he endorsed Clinton in an open letter to voters this week that argued weakening Clinton in the primary brings Trump closer to control over the nation's nuclear codes.

Clinton's address underscored for Democrats and independents voting in the party's primary “the intense peril created by the prospect that Donald Trump could get anywhere near the White House,” said Rep. Adam Schiff, a California Democrat supporting Clinton.

“She showed she is in the best position to go toe-to-toe with him,” Schiff said.

It marked a notable change in tone for Clinton, who for weeks has vacillated between limited engagement with Trump and leaving that work to her surrogates, as the former secretary of state sought to stay above the fray.

On Thursday, Clinton did not hold back. She mocked Trump relentlessly, while at the same time patiently laying out the thinking behind key diplomatic and national security decisions she has taken part in — and why voters should question whether Trump has the intellectual capacity and mental stability to be trusted to make such decisions.

“It is not hard to imagine Donald Trump leading us to war just because someone got under his very thin skin,” she said, then began quoting some of the remarks Trump has made that national security experts find alarming.

“This is a man who said more countries should have nuclear weapons, including Saudi Arabia,” Clinton said. “He has also said, ‘I know more about (the Islamic State) than the generals do. Believe me.' You know what? I don't believe him.”

evan.halper@tribpub.com