The scope and scale of Hillary Clinton's victories on Wednesday ameliorates much of the pressure that she has been under to pander to Bernie Sanders and his supporters.

California was the biggest delegate prize of 2016 for Democrats. Sanders spent the better part of the past month camped out there. And Clinton beat him by 13 points - or nearly half a million votes.

She won the second most valuable prize available on Wednesday, New Jersey, by 26 points. And she defeated Sanders in New Mexico and South Dakota.

The Democratic coalition will ultimately unify behind Clinton - as long as she pays a modicum of respect to Sanders, which she will - because the liberal base does not want Donald Trump to become president.


And Clinton benefits enormously from growing concerns among independent voters about the presumptive Republican nominee.

Sanders, who won the small states of Montana and North Dakota, promised he will "continue to fight" for delegates. "The struggle continues," he declared to a crowd of 3300 in Santa Monica. "We are going to fight hard to win the primary in Washington DC (on June 15) and then we take our fight for social, economic, racial and environmental justice to Philadelphia, Pennsylvania."

But he also acknowledged that the path ahead is "very steep". And an aide said his campaign plans to part ways with many staffers, in particular people who work on advance and field operations. His staff plans to have candid conversations with the candidate aboard the campaign plane on the flight from Los Angeles to Burlington, Vermont. Then, tomorrow, he'll sit down with President Barack Obama in the Oval Office.

The maths are undeniable: Clinton has prevailed. "Even if superdelegates hadn't existed this year, she still would have won the nomination," Washington Post writer Dave Weigel notes.

Once again, Hillary excelled in higher-turnout primaries and bigger states with more delegates while Bernie did best in a lower-turnout caucus with relatively few delegates on the line.

Clinton unexpectedly won the South Dakota primary, even as she lost in the North Dakota caucuses. "In caucus states, he's averaging over 60 per cent of the vote. In primaries, he averages just under 43 per cent. He's won 71 per cent of caucuses; Clinton has won 72 per cent of primaries," Washington Post writer Philip Bump notes.

Sanders hoped a victory in California and some surprises elsewhere would give him an argument to pull superdelegates away from Clinton. Neither happened. And now he has little justification for continuing his quixotic quest, with the exception of trying to maximise his leverage.

Obama is committed to keeping the White House in Democratic hands.

The White House released a statement to declare Clinton the winner, announce that Obama will meet Sanders and reveal that POTUS called both candidates. "The President congratulated both candidates for running inspiring campaigns," Josh Earnest said. "The President congratulated Secretary Clinton for securing the delegates necessary to clinch the Democratic Nomination for President. Her historic campaign inspired millions and is an extension of her lifelong fight for middle-class families and children."

Earnest said Sanders requested the meeting with Obama, and it will take place at the White House: "The President looks forward to continuing the conversation with Senator Sanders about how to build on the extraordinary work he has done to engage millions of Democratic voters, and to build on that enthusiasm in the weeks and months ahead."

A woman listens to Democratic presidential candidate Senator Bernie Sanders in Santa Monica, California, on Wednesday. Photo / AP
A woman listens to Democratic presidential candidate Senator Bernie Sanders in Santa Monica, California, on Wednesday. Photo / AP

Beyond Obama, a handful of other Democrats are also pursuing unity. Vice-President Joe Biden, Senator Elizabeth Warren, and Senate Minority Leader Harry Reid, are all working to bring both sides together: Obama and White House political director David Simas, as well as Warren and Reid, have been in communication with both camps to lay the foundation for an eventual coming together, according to several senior Democrats. Sanders also plans to meet Reid on Capitol Hill.

The growing number of Republican defections from Trump show that this will not be as much of a base election as the last several presidential contests. If Clinton can win over independents and centre-right Republicans who are alarmed by Trump, she will win the presidency.

Illinois Republican Senator Mark Kirk withdrew his endorsement. "I cannot and will not support my party's nominee for president," he said.

1 15,729,812 Hillary Clinton
2 13,300,472 Donald Trump
3 12,009,309 Bernie Sanders

Kirk's not going to vote for Hillary. He said he'll write in David Petraeus. But his statement puts growing pressure on other GOP incumbents, especially in blue and purple states, to follow suit.

Nevada Republican Governor Brian Sandoval, who is Hispanic and a former federal judge, called Trump's comments about Gonzalo Curiel "indefensible". After saying last month he planned to vote for Trump, he said yesterday: "I support the Republican Party and will continue to help elect strong Republican leaders in Nevada but at this time I cannot say I will definitely vote for Mr Trump."

A Republican state senator in Iowa formally left the GOP to protest against Trump's recent round of offensive remarks. "I will not stand silent if the party of Lincoln and the end of slavery buckles under the racial bias of a bigot," David Johnson told the Des Moines Register.

And Wednesday's primary results show trepidation about Trump among Republican base voters. More than a month after the GOP contest effectively ended, Trump got just 67 per cent in South Dakota, 71 per cent in New Mexico, 74 per cent in Montana and 81 per cent in New Jersey. In California, with ballots still being counted, Trump is pulling about three-quarters of the vote. John Kasich got 11 per cent and Ted Cruz got 8 per cent.

Clinton has surmised that the easiest path to victory in this environment is turning the election into a referendum on Trump.

The campaign is launching a "Republicans against Trump" initiative aimed at making inroads. "Trump is not qualified to be president," a pledge on the site reads. "He does not represent my beliefs as a Republican and, more importantly, my values as an American. He does not speak for me and I will not vote for him."