Hillary Clinton’s refusal to keep a promise to debate Sen. Bernie Sanders in California was obviously based on her assumption that the nomination is hers and that there is no need to risk further exposure in an uncontrolled setting.

If her premise were true, it might make sense from a purely strategic standpoint, even if it would represent a flat-out retreat from a pledge she made in February to participate in a California debate in May. The Clinton campaign no doubt figured that whatever flak she might encounter for the broken promise would be preferable to the potential of a gaffe or awkward debate moment that might go viral.

However, a Public Policy Institute of California poll released late Wednesday suggested that state voters do not necessarily agree that the Democratic primary is a settled issue.

The poll showed Clinton and Sanders in a dead heat, with the former secretary of state at 46 percent and the Vermont senator at 44 percent among likely Democratic primary voters. It also showed her less than invincible in a general election, with a 49 to 39 percent lead over Donald Trump in a state where GOP registration is just 28 percent.

Sanders, who had been pressing Clinton to keep her debate commitment, said she “may want to be not quite so presumptuous about thinking that she is a certain winner.”

The Chronicle had been prepared to partner on the California debate with Fox News, which proved superior to other networks in instilling substance and control into primary debates. The Clinton campaign also has been unresponsive to repeated requests to meet with our editorial board. Sanders did so on May 10, taking all questions and allowing the session to be live-streamed and archived on The Chronicle’s Facebook page.

Clinton is a prohibitive favorite to attain the party’s nomination before its Philadelphia convention. Still, Californians deserve more than a succession of rallies, photo opportunities and fundraisers from a major presidential candidate. They deserve a chance to fully compare and contrast the two remaining candidates on everything from the federal reach on state issues such as water and high-speed rail to their differing visions of the role of a global superpower.

Exit polls throughout the primary season have shown that questions about Clinton’s “honesty” and “trustworthiness” remain her biggest challenges as she prepares for a general election against a billionaire saddled with daunting negatives of his own. Her broken promise to debate in California is not going to assuage those concerns among skeptical voters who just might be tempted to send a message to Clinton on her final glide path to the nomination.