Washington — Hillary Rodham Clinton has locked up public support from half of the Democratic insiders who cast ballots at the party's national convention, giving her a commanding advantage over her rivals for the party's presidential nomination.

Clinton's margin over Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley is striking. Not only is it big, but it comes more than two months before primary voters head to the polls — an early time in the race for so many of the people known as superdelegates to publicly back a candidate.

"She has the experience necessary not only to lead this country, she has experience politically that I think will help her through a tough campaign," said Unzell Kelley, a county commissioner from Alabama.

"I think she's learned from her previous campaign," he said. "She's learned what to do, what to say, what not to say — which just adds to her electability."

The Associated Press contacted all 712 superdelegates in the past two weeks, and heard back from more than 80 percent. They were asked which candidate they plan to support at the convention next summer.

The results:

Clinton: 359.

Sanders: 8.

O'Malley: 2.

Uncommitted: 210.

The 712 superdelegates make up about 30 percent of the 2,382 delegates needed to clinch the Democratic nomination. That means that more than two months before voting starts, Clinton already has 15 percent of the delegates she needs.

That sizable lead reflects Clinton's advantage among the Democratic Party establishment, an edge that has helped the 2016 front-runner build a massive campaign organization, hire top staff and win coveted local endorsements.

Superdelegates are convention delegates who can support the candidate of their choice, regardless of who voters choose in the primaries and caucuses. They are members of Congress and other elected officials, party leaders and members of the Democratic National Committee.