Clinton has delegates to win Democratic nomination: AP survey

Striding into history, Hillary Clinton will become the first woman to top the presidential ticket of a major US political party, capturing commitments from the number of delegates needed to win the Democratic nomination.

Clinton's rise to presumptive nominee arrived nearly eight years to the day after she conceded her first White House campaign to Barack Obama. Back then, she famously noted her inability to "shatter that highest, hardest glass ceiling."

Campaigning this time as the loyal successor to the nation's first black president, Clinton held off a surprisingly strong challenge from Vermont Senator Bernie Sanders.

He mobilised millions with a fervently liberal message and his insurgent candidacy revealed a deep level of national frustration with politics-as-usual, even among Democrats who have controlled the White House since 2009.

The former secretary of state, New York senator and first lady reached the 2,383 delegates needed to become the presumptive Democratic nominee on Monday with a decisive weekend victory in Puerto Rico and a burst of last-minute support from superdelegates.

Those are party officials and officeholders, many of them eager to wrap up the primary amid preference polls showing her in a tightening race with presumptive GOP nominee Donald Trump.

Clinton has 1,812 pledged delegates won in primaries and caucuses. She also has the support of 571 superdelegates, according to an Associated Press count.

The AP surveyed all 714 superdelegates repeatedly in the past seven months, and only 95 remain publicly uncommitted. Sanders plans to make the case to superdelegates that he is better positioned to beat Trump in November.

While superdelegates can change their minds, those counted in Clinton's tally have unequivocally said they will support her at the party's summer convention.

Since the start of the AP's survey in late 2015, no superdelegates have switched from supporting Clinton to backing Sanders.

"We really need to bring a close to this primary process and get on to defeating Donald Trump," said Nancy Worley, a superdelegate who chairs Alabama's Democratic Party and provided one of the last endorsements to put Clinton over the top.

Clinton had a muted reaction to her claim on the nomination Monday night as she campaigned in California. She told a cheering crowd she was on the brink of a "historic, unprecedented moment," but said there was still work to be done in the six states to vote today.