President Obama made the call a day after Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE vowed to fight Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE all the way to the Democratic convention in Philadelphia.

The tense primary fight between the heavily favored Clinton and her liberal challenger had already gone on much longer than anyone had anticipated.

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While Clinton had a clear lead in votes and pledged delegates, Sanders’s most vocal supporters were showing no signs of giving in. Despite Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE’s stumbles on the GOP side, Democrats worried their presidential candidate could be hurt if their party were too divided in the fall.

It’s not clear what Obama said to the Vermont senator during the Sunday conversation.

But a day later, Sanders had changed his tone, saying he would “assess” his path to victory following California’s primary.

The phone call is just one example of Obama’s efforts to exert influence in the Democratic primary.

Obama had to tread carefully in a fight that pitted Sanders against his own former secretary of State. From the beginning, Obama was seen as a Clinton supporter, but he’s managed to emerge from the battle with praise from both camps.

“Look, the president has been very even-handed throughout this process,” Jeff Weaver, Sanders’s combative campaign manager, said Tuesday on MSNBC. “That’s greatly appreciated.”

Weaver has been starkly critical of Democratic National Committee Chairwoman Debbie Wasserman Schultz, accusing her of tilting the scales against Sanders. But he lauded Obama for “stay[ing] out and letting the voters have their say,” calling it “a real mark of leadership on his part.”

Obama is clearly eager to get engaged in a general election contest against Trump, the presumptive Republican nominee.

He’s laid into the Republican at times, showing he’ll be an effective surrogate for a Democratic nominee.

It’s an interesting position for Obama — and one no president has been in for some time. He’s likely to enter the fall as a popular president hitting the campaign trail to win what some may see as a third term for his presidency.

Keeping an air of neutrality in the tense Sanders-Clinton battle will help him make the case for Democrats in the fall, and gives him credibility in brokering peace between the two candidates right now.

“He can come across as an honest broker between the Clinton and Sanders people because he was never overtly supportive of the Clinton campaign,” Democratic strategist Brad Bannon said of Obama.

“He was never really obvious in saying, ‘you should vote for Hillary Clinton’ or ‘she should be the next president.’ ”

While Democratic leaders in Congress have formally endorsed Clinton, Obama has not.

And on Wednesday, after Clinton won a huge victory in California’s primary, Obama did not push Sanders from the race even as MoveOn and Sanders allies in Congress suggested the end is near.

Vice President Biden said Sanders should “have the opportunity to decide on his own” about ending his bid.

“I think that’s his call,” he said, according to CNN.

White House press secretary Josh Earnest echoed Biden, saying on Wednesday that Sanders has “more than earned the right to make his own decision” about his campaign’s future.

Current and former Obama advisers expect the president to use Thursday’s meeting to lay the groundwork for reconciliation — not an easy task considering the combative tenor of the Democratic campaign.

Sanders repeatedly mocked Clinton for refusing to release transcripts of paid speeches she’s given to large corporations, including Goldman Sachs.

Clinton, meanwhile, questioned the longtime Independent senator’s commitment to the party and accused him of being soft on gun control.

The battle between their supporters has been even more intense. A chaotic outburst of screaming and cursing by Sanders backers at last month’s Nevada state party convention spurred fears of an all-out revolt at the Democratic National Convention in July.

Obama finds himself in a position as healer in large part thanks to a series of good decisions about where and when to wade into the campaign.

It wasn’t easy, and the president often strained to remain neutral.

Obama and his aides have been peppered with questions about the election for months and have generally gone out of their way to praise both candidates.

Earnest volunteered to reporters on Wednesday that Obama and Sanders, who are not known to be close, have spoken three times in the last month.

He declined to say how many times Clinton has spoken with the president. But eager to play up her ties with Obama, Clinton said Tuesday she has “continually talked” with Obama during the campaign.

White House political director David Simas has spoken to both campaigns about coming together ahead of the general election, according to a person familiar with the discussions. Those conversations have ramped up in recent days.

Obama has not always done a good job of hiding his opinions about the primary.

He suggested in a January interview with Politico that he believes Clinton best understands what it takes to occupy the Oval Office, suggesting that Sanders was simply a “bright, shiny object” for voters who are tired of his former secretary of State.

Those comments forced Obama to do damage control, including meeting with Sanders a week later for 45 minutes in the White House.

All seemed to be forgiven when Sanders emerged from the discussion saying that Obama wasn’t “tipping the scales toward Secretary Clinton.”

But after a string of primary losses in mid-March, Obama once again had a moment of candor during a fundraiser in Texas, when he told donors the time was coming to rally around Clinton.

And his staff rose to Clinton’s defense when she came under attack from Sanders as being unqualified to lead the nation.

When asked Tuesday how persuasive Obama would be in convincing Sanders to embrace party unity, Weaver demurred.

“Bernie Sanders really answers to those people, the people who voted for him, the people who support him, the people in the grass roots,” he said. “Ultimately, at the end of the day, any decision he makes will be with those people in mind.”