But even as Sanders vows to fight on, he and presumptive nominee Hillary Clinton are making a truce.

The two friends-turned-opponents plan to meet face-to-face on Tuesday night for the first time in months after the polls close for the D.C. primary. They will begin to sort out their differences: Sanders will lay out what he wants from the party; Clinton will ask for Sanders’ support.

Meanwhile, top aides for the two campaigns have been in frequent contact in recent days. Sanders’ allies and Clinton’s are cordially working together to hash out a platform for the Democratic National Convention in Philadelphia. Sanders’ plan to pick off superdelegates from Clinton has lost momentum, Democrats say, and his allies are focused on winning platform concessions at the Democratic convention.

Clinton sounds optimistic that they will make peace. “I’m looking forward to working with [Sanders] to achieve our common goal, which is to defeat Donald Trump,” she said last week on CNN. “And Senator Sanders has said he’ll work every day, every week to see that happen.”

How and when Sanders and Clinton peaceably wind down the primary campaign over the next few days and weeks will be crucial for unifying the Democratic Party.

Sanders would be a major aid to Democrats and to Clinton in the fall if he were to write to his email list and bring his supporters on board. Sanders has attracted a cohort of younger and independent voters that Clinton and the Democratic Party desperately hope to adopt.

“Bernie’s going to be very good for the party,” said Senator Harry Reid, who has been in discussions with Sanders.

It is a delicate balance: Clinton wants to win Sanders’ support quickly and enlist him to defeat Trump, but she is wary of pushing him too quickly and asking too much of the famously cantankerous contrarian.

So far, much of the outreach has come from Clinton’s camp. It was Clinton who phoned Sanders last Tuesday after his crushing loss in California, reversing the usual custom of the loser calling the victor.

Clinton aides are playing at appeasement, hoping not to aggravate the Vermont Senator before the convention. Robby Mook, the Clinton campaign manager, and Jeff Weaver, Sanders’ campaign manager, have spoken multiple times over the past week. The Clinton campaign’s Charlie Baker and Sanders’ Mark Longabaugh, both of whom negotiated a contentious debate schedule, have also been in regular contact.

Mook has been a key player in thawing relationships between the two campaigns, sources close to the discussions say, serving as a conduit between Sanders aides and Clinton. Mook is the closest person to Clinton who is communicating regularly with Sanders’ campaign, and Sanders’ aides respect and trust him.

Clinton’s charm offensive is public too. During her victory speech last Tuesday in Brooklyn, Clinton openly backslapped Sanders. “SenatorSanders, his campaign, and the vigorous debate that we’ve had about how to raise incomes, reduce inequality, increase upward mobility have been very good for the Democratic Party and for America,” she said.

When Mark Ruffalo, the actor and Sanders surrogate, wrote on Twitter, “Chin up @BernieSanders supporters. we are doing impossible things together. We too have won historically and are just getting started!” communications maven for the Clinton campaign Jennifer Palmieri chimed in. “Truth,” she wrote.

Truth https://t.co/WLSTojPXLN

— Jennifer Palmieri (@jmpalmieri) June 8, 2016

There have been some tense moments, however. At a Democratic Party hearing last week held by the 15-person committee drafting the party’s platform, Sanders surrogate and activist Dr. Cornel West had a heated exchange with Clinton surrogate Robert Wexler, a former Florida Congressman, over the party’s stance toward Israel.

“A commitment to security for our precious Jewish brothers and sisters in Israel can never be predicated on an occupation of precious Palestinians,” West said. “I would oppose the use of the word occupation for the very reason it undermines our common objective,” Wexler argued back.

At another point, West challenged President Obama’s former attorney general, Eric Holder, asking him why more executives in the finance industry were not prosecuted after the 2008 meltdown.

Sanders and his top allies met at his home in Burlington on Sunday to discuss a plan going forward. West, environmental activist Bill McKibben, Arizona Representative Raúl Grijalva, Oregon Senator Jeff Merkley, former NAACP president Ben Jealous, and Hawaii Representative Tulsi Gabbard and others are expected to attend.

Some Clinton aides have felt impatient to move on. They have said publicly for months that Sanders would be soundly beaten. Now armed with endorsements from President Obama, Vice President Joe Biden and Massachusetts Senator Elizabeth Warren, Democrats with prestige in the party’s progressive wing, Clinton and her staff believe party unity is at hand.

There is an understanding, however, in all their interactions with the Sanders campaign that they have to be patient. Sanders aides are encouraging Clinton to give Sanders time, saying that the Senator needs to be wooed and enticed, not forced.

Clinton “looks forward to the opportunity to discuss how they can advance their shared commitment to a progressive agenda, and work together to stop Donald Trump in the general election,” said a Clinton official.

Clinton is more popular in her party than Obama was eight years ago after winning the primary: her favorable-unfavorable rating among Democrats is 77-21, according to a YouGov/Economist poll, compared with 59-21 for Obama at this point in 2008, a CBS/New York Times poll showed.

Even as Sanders last Thursday at Robert F. Kennedy Stadium in Washington continued to preach a gospel of political revolution, he did not attack Clinton head-on. And while many of Sanders’ supporters in the audience hoped he would fight for $15 minimum wage, single-payer health care and free college at the convention, they knew he would eventually throw in the towel.

“It’s going to be a general-election matchup between her and Donald Trump, so I think the best thing that Bernie and his camp and all his supporters here can do is try to really push for these issues on the Democratic platform,” said Daniel Riley, a 28-year-old Sanders supporter. “I’m here as a Bernie supporter and someone that likes his message, but I’m realistic to the fact that the party has already picked Hillary.”

— With reporting by Julissa Higgins

This article is published in partnership with Time.com. The original version can be found here.