Hillary Clinton's campaign has begun showing frustrations with Sen. Bernie Sanders (I-Vt.), urging him to find a way to peacefully wind down his presidential campaign amid the near certainty that she will have the delegates needed for the nomination.

The frustrations are not so much that Sanders has remained in the race to this point -- which Clinton staffers universally say is his right to do -- but that he's continued to chip at his Democratic opponent rather than allow her an easier turn to the general election. In the past week, Sanders went after Clinton for her vote on the Iraq War, just moments after she delivered what was widely seen as a blistering foreign policy critique of Donald Trump. Then, the senator questioned the donations the government of Saudi Arabia made to the Clinton Foundation -- a subject that is catnip for conservatives but Sanders had largely so far avoided.

Clinton's camp has been more annoyed by Sanders' persistent questioning of her motives and ethical compass, usually in the wake of Clinton trying to court Republicans or Wall Street Wall Street donors repulsed by Trump. What Sanders has deemed a moral compromise, Clinton's aides see as pragmatic politics.

"If Bernie Sanders or his supporters think the recipe for success in America is to cut off everybody who doesn't agree with you, then I'm losing the distinction between that and Donald Trump, and I don't think anybody in Bernie Sanders' camp is like Donald Trump," Clinton's top adviser, Joel Benenson, told The Huffington Post in an interview last Friday. "I think they believe we have to make progress in people's lives, and that's why Bernie Sanders says we have to do everything we can to stop Donald Trump."

In some respects, Benenson's grievance echoes a broadly shared concern among Democrats that the important window in which to operate against Trump is closing. In April, David Plouffe, President Barack Obama's first campaign manager, warned that it would be a "feat of epic political malpractice" for Clinton to start the general election after the last states voted on June 8. She has certainly avoided that self-inflicted wound: The campaign has already begun building the equivalent of a 50-state strategy for the fall, an aide said. But many hoped that she'd be well beyond having to worry about a discontented base at this juncture, let alone through the convention in July.

Still, Benenson's comments are rare for their directness. A close campaign consultant said that the plan is to "continue to be patient" with Sanders, maintaining a positive message while outsourcing the sharper material to surrogates, as exemplified by Clinton herself on Monday.

"We've got to be unified going into the convention and coming out of the convention to take on Donald Trump," Clinton tells reporters in CA. — Philip Rucker (@PhilipRucker) June 6, 2016

Aides also don't anticipate that this primary drama will play out to the convention, believing talk within Sanders' universe of a Philadelphia showdown is largely bluster.

"I hear what Jeff Weaver is saying," Benenson said of Sanders' hard-charging campaign manager. "I'm going to take Senator Sanders at his word that he wants to help defeat Donald Trump, and I think Senator Sanders knows the way to do that is to unite the Democratic Party. If they are not in that lane, that would be surprising because the stakes are pretty high."

I'm going to take Senator Sanders at his word that he wants to help defeat Donald Trump, and I think Senator Sanders knows the way to do that is to unite the Democratic Party. If they are not in that lane, that would be surprising because the stakes are pretty high. Joel Benenson, Clinton's top strategist.

The pressure certainly will mount on Sanders after Tuesday. The New York Times reported that Obama is itching to get out on the trail to go after Trump, presumably as a surrogate for Clinton. On the Hill, an aide confirmed that Democratic leadership will ramp up the outreach to Sanders to find a graceful path to end the primary after Tuesday.

And then there is the issue of math. By Tuesday night, Clinton will almost assuredly have a majority of pledged delegates. She only needs 33 percent of those awarded on Tuesday (roughly 250) to get there. Though that won't guarantee her the nomination, since superdelegates also count, it will remove a critical, psychological hurdle. At that juncture, Sanders' argument that superdelegates should switch their support for Clinton against the will of the voters will no longer be theoretical. And even his ideological compatriots in the Senate -- including Elizabeth Warren (D-Mass.) and Jeff Merkley (D-Ore.) -- have said they oppose that outcome.

Privately, Sanders aides say he is not blindly optimistic about the task or path ahead. But as Sanders himself hinted on Monday, he is more inclined to continue moving forward should he have so much as a decent showing in California's primary.

Sanders adds that he will "certainly" campaign in Washington, DC ahead of that contest in mid-June — Robert Costa (@costareports) June 6, 2016

Those same aides warn that efforts to push him out of the race -- whether real or perceived -- will most likely backfire.

"He is not beholden to anybody. There aren't money people who are going to be upset [if he stays in]; there aren't finance people who are going to be upset, because that's not the nature of his candidacy," said a top Sanders aide. "He built something from nothing. ... And that can be used for a good purpose. But the way to make that happen is if he feels he is being treated with respect. When you try to pressure him to do anything, that is the wrong approach."

Sanders, indeed, is a candidate over which there are relatively few leverage points: He only recently became a Democrat and enjoys a fundraising apparatus independent of long time donors. As a result, producing a smooth ending to the primary will probably take more carrots than sticks. The party has had trouble with that balance. However, a recent decision by the Democratic National Committee to accommodate many of Sanders' choices for the committee tasked with drafting the party platform did not go unappreciated.

Neither did Clinton's recent speech eviscerating Trump. While Sanders may have responded with a dig at Clinton's vote to authorize the Iraq War, internally, campaign aides were impressed by her ability to diminish the Republican nominee and reassure superdelegates.

"I think it helped her," said the top Sanders aide. "I don't think one speech is big enough to switch a state like California, [but] it was a reassurance speech for the most important audience for her, which is the people who are ultimately going to decide the nomination. She gave it, and it went over well."