Democratic Party leaders are sweating over the prospect of Democratic nominee Bernie Sanders - and also a fractured party.

The New York Times reported Thursday that former President Bill Clinton has been calling old friends and venting about Sanders, fearing his nomination could wipe out the party in the general election. Sanders was Hillary Clinton's primary opponent in 2016.

Former President Barack Obama, on the other hand, signed on to a party fundraising email Thursday afternoon that's central theme was all about unity.

BERN DOWN THE HOUSE: The New York Times reported Thursday that former President Bill Clinton has been calling old friends and venting about the prospect of a Democratic nominee Bernie Sanders, who Clinton thinks will tank the party in November

Former President Barack Obama doubled down on what The Times reported, as he signed onto a fundraising email for Democrats Thursday that had the central theme of party unity. Some Democrats have asked Obama to broker a truce between Sanders and other candidates

Democrats are nervous that Bernie Sanders could ruin the party's chances of winning the White House in November. They are also fearful that Sanders won't get enough delegates to win the nomination outright, leading to a brokered convention

'We must throw our unified support behind our future nominee and Democrats across the country so that, no matter who wins, they'll have the resources they need to win,' Obama wrote, asking party members to finance the Democratic Unity Fund.

'Committing to party unity is not always easy,' Obama's note continued. 'But it is what this moment in our politics - and our history - demands of us.'

'There is too much at stake to let division and hatred win this race,' the ex-president added.

Obama was doubling down on the Times' reporting, which said that he had no interest in getting involved in the current Democratic primary race - and viewed himself as a party leader who could help heal the wounds if a rough nomination fight splinters the party badly.

Obama has been asked by some party members, according to The Times, to broker a truce between Sanders and some of the moderate candidate, which include Obama's Vice President Joe Biden. The ex-president was also asked to broker a truce between Sanders and the more establishment wing of the party.

He's declined.

One big fear is that Sanders will enter the convention with a plurality of delegates, but not enough to win the nomination outright.

If one candidate doesn't have a majority of pledged delegates on the first ballot, superdelegates - party officials, including members of Congress - can voice their pick on the second ballot.

Also on the second ballot, pledged delegates can defect to another candidate.

Sanders and his team are arguing that if Sanders has the most pledged delegates - from winning primaries and caucuses - but is short of a majority, he should still get the nomination.

Most Democrats disagree.

The Times interviewed 93 superdelegates and only nine held Sanders' view.

A number of them had zany suggestions on how the Democrats could build a White House winning team from the embers of a Democratic National Convention floor fight.

Some suggested nominating a candidate on the floor who decided against running for president - or already dropped out.

White knight candidates included Sen. Sherrod Brown, an Ohio Democrat who could bring along his swing state, or Sen. Kamala Harris, who dropped out before nominating contests started earlier this month.

William Owen, a DNC member from Tennessee interviewed by The Times, floated picking Michelle Obama as vice president.

'She's the only person I can think of who can unify the party and help us win,' he told the newspaper.

'This election is about saving the American experiment as a republic. It's also about saving the world. This is not an ordinary election,' Owen said.