Bernie Sanders finally comes out in support of Clinton

Defeated in the presidential nomination race, Democrat Bernie Sanders on Tuesday endorsed former rival Hillary Clinton for president in a display of party unity, describing her as the best candidate to fix the United States' problems and beat Republican Donald Trump in the 8 November election.

With Clinton nodding in agreement beside him, Sanders put aside their bitter campaign for the nomination and said she would take up the fight to ease economic inequality, make college more affordable and expand healthcare coverage for all Americans.

"This campaign is about the needs of the American people and addressing the very serious crises that we face, and there is no doubt in my mind that, as we head into November, Hillary Clinton is far and away the best candidate to do that," he told a raucous crowd in Portsmouth, New Hampshire, that included plenty of vocal Sanders supporters.

"I intend to do everything I can to make certain she will be the next president of the United States," the US senator from Vermont said.

His endorsement, five weeks after Clinton became the presumptive Democratic presidential nominee, brought the most prominent holdout in the party's liberal wing into her camp. Sanders threw Clinton his support less than two weeks before the Democratic National Convention in Philadelphia, where she is to be formally nominated.

"I can't help but reflect on how much more enjoyable this election will be now that we are on the same side," Clinton said of Sanders. "Thank you, Bernie, for your endorsement, but more than that, thank you for your lifetime of fighting injustice."

Rigged system: Trump
Trump ridiculed the move in a series of Twitter posts, saying Sanders had abandoned the supporters who flocked to his campaign to rein in Wall Street and get big money out of politics.

"Bernie Sanders endorsing Crooked Hillary Clinton is like Occupy Wall Street endorsing Goldman Sachs," Trump said on Twitter.

In a statement, the Trump campaign said Sanders was now officially part of the rigged system the senator had criticized during his long primary battle with Clinton.

"Bernie's endorsement becomes Exhibit A in our rigged system - the Democrat Party is disenfranchising its voters to benefit the select and privileged few," said Stephen Miller, a senior policy adviser to Trump.

In a Reuters/Ipsos opinion poll released on Tuesday, Clinton extended her lead over Trump to 13 percentage points, up from 10 points at the end of last week.

The former US secretary of state hopes the Portsmouth appearance with Sanders will help her win over his supporters, some of whom held Sanders signs at the rally and chanted his name. In recent Reuters/Ipsos polling, only about 40 per cent of Sanders backers said they would back Clinton, and the crowd at Tuesday's rally made it clear she still had work to do.

"I am absolutely certain I will not vote for Hillary Clinton," Gale Bailey, a Sanders supporter and an unemployed graphic designer from Rochester, New Hampshire, who attended the rally in a Sanders T-shirt, told Reuters.

"She's a crook, and I'm not going to vote for a crook," Bailey said, adding that she would write in Sanders' name on the November ballot.