For months, two dangers have hovered over Hillary Clinton's presidential campaign – the possibility of criminal proceedings resulting from the investigation into her email practices and the risk that large numbers of Bernie Sanders supporters would desert her in the fall.
Last week, the first of those evaporated with a statement by FBI Director James B. Comey that sharply criticized her, but closed the door on prosecution. Tuesday, the second risk diminished greatly with a sentence from Sanders at a rally in a crowded high school gymnasium here.
“I am endorsing Hillary Clinton,” Sanders declared to cheers from a couple of thousand partisans. “She must become our next president.”
One rally, of course, will not bring every Sanders voter over to Clinton – some will not shift for weeks, others never will. But Sanders' words, which were noticeably more enthusiastic than many Democrats had expected, will almost certainly hasten a party unification process that polls indicate is already well underway.
"This campaign is about the needs of the American people and addressing the very serious crises that we face," Sanders said as Clinton stood nodding at his side. "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."
Although long-awaited and, to some extent, anticlimactic, since many of Sanders' backers already have moved Clinton's way, the rally was nonetheless a positive moment that the Clinton campaign had badly wanted and worked hard to achieve. It opens the way for a nominating convention later this month that can showcase party unity, in likely contrast to the GOP convention that begins next week.
Sanders dispelled doubts about how strongly he would back the woman who had beaten him by delivering a half-hour litany that not only denounced Donald Trump, the presumptive Republican nominee, but praised the former secretary of State, saying repeatedly that "Hillary Clinton understands" the key issues he campaigned on.
On issues including healthcare, the minimum wage and aid for college students, he stressed how much he and Clinton agreed – a sharp turnaround from months of detailing their differences.
He said he would "go to every corner of this country" to try to ensure her election.
Clinton returned the favor, inserting into her standard stump speech a strong endorsement of Sanders' position on an issue on which they have differed – one that the Vermont senator had not mentioned. In her administration, she said, the U.S. would say "no to unfair trade deals … including the Trans-Pacific Partnership."
President Obama has asked Congress to approve the massive trade pact, which Clinton had praised while it was being negotiated. Earlier in her campaign, she said the final agreement fell short of her standards and she would not support it, but many of Sanders' supporters have doubted her commitment.
Thanking them, Clinton pledged, "You will always have a seat at the table when I am in the White House."
Not everyone in the crowd was convinced. Earlier in the event, some pro-Sanders hecklers jeered Gov. Maggie Hassan when she praised Clinton.
And among Sanders' delegates to the Democratic convention, some said they were still not sure they could bring themselves to vote for her.
"I still can't speak to that," said Natalie Higley, a 23-year-old delegate from Lakeport, in Northern California. "I think he's doing what he has to do," she said of Sanders.
Nominating Clinton "is going to greatly reduce the participation in the Democratic Party, to elect a candidate who has some of the lowest favorable ratings in history, who is squeaking by, barely beating Trump in November. I think they are committing suicide, honestly," she said.
In an email to supporters, Sanders acknowledged "that some of you will be disappointed" by the decision to endorse Clinton. But, he said, Clinton had embraced "the most progressive Democratic platform in the history of our country," in part because of the pressure exerted by the 13 million people who had voted for him in the Democratic primaries.
If Trump were to win, not only would none of those policies be adopted, his victory would be "a devastating blow to all that we are fighting for," Sanders warned.
That was a persuasive argument for Robert Nelson, a retired scientist from Pasadena who is also a Sanders delegate.
"This election is not about Hillary Clinton anymore. This election is about Donald Trump," Nelson said. "Donald Trump represents the true threat of fascism, and fascism is a very, very dangerous thing."
The joint appearance here, in the state whose primary did more than any other to propel Sanders into the role of a true threat to Clinton, came after weeks of negotiations and careful choreography.
Sanders moved cautiously in Clinton's direction – too slowly in the eyes of some Democrats – as her campaign edged toward his positions on major issues, most notably proposals to increase federal help with the cost of going to college and expanded efforts to cut the cost of healthcare.
Clinton's new healthcare proposal, announced over the weekend, included a $40-billion increase in money for community health centers, a priority for Sanders, and a renewed call for the sort of "public option" insurance plan for which President Obama failed to secure when Congress passed the Affordable Care Act in 2010.
By now, polls show that most Sanders supporters already have made their peace with voting for Clinton – spurred on by the prospect of Trump. Democrats are more unified than they were at this point in 2008. That relative party unity is a big part of the reason Clinton has held a consistent lead over Trump of about 4 to 6 percentage points in polling averages since the start of June.
But a significant minority of Sanders voters have resisted calls to fall into line behind Clinton, some feeling that her policies are not far enough to the left to suit them, others opposed to her personally.
Disaffected Sanders voters, especially men, provide a notable chunk of support for the Libertarian nominee, former New Mexico Gov. Gary Johnson.
If a Sanders endorsement brings more of those voters over to Clinton's side, her lead over Trump could be expected to grow by another percentage point or two nationally – enough potentially to swing some close-fought states in her direction.
In part to engineer that outcome, the two sides spent considerable time over the last several weeks negotiating steps toward unity. Clinton's campaign manager, Robby Mook, and his counterpart from the Sanders camp, Jeff Weaver, took the lead, said a Clinton campaign aide, speaking on condition of anonymity to talk about the private negotiations.
The two met for nearly two hours in early June after Clinton and Sanders got together at a downtown Washington hotel. They followed up with a dinner in Vermont – a burger for Weaver and salad for Mook – and have been in near daily contact by email and text messages, the campaign aide said, noting that Sanders' wife, Jane, also played a major role in negotiations.
From early on in the discussions, it was clear that Sanders was focused mainly on specific issues that he could influence Clinton on and that Clinton was willing to accommodate him on at least some of those.
That contrasts with some previous elections in which defeated candidates needed help retiring large debts or wanted jobs for supporters. The Clinton campaign has, however, begun hiring some key Sanders operatives, including a new director of on-campus political organizing.
Over the weekend, the Democratic platform committee finished drafting the party's positions for this election. Sanders' top aide at the committee said his side had gotten 80% of what it wanted.
Staff writers Seema Mehta in Los Angeles and Chris Megerian in Sacramento contributed to this report.
For more on politics and policy, follow me @DavidLauter
2:46 p.m.: This article was updated throughout with new comments and details.
9:48 a.m.: This article was updated with comments from Clinton and Sanders.
8:41 a.m.: This article was updated with Sanders' endorsement.