The response from Clinton's supporters in the Senate: It's OK with them.
Top Democratic leaders and prominent Clinton backers say they have no issue with the Vermont independent's continued presence in the race, even as Sanders' quest for the nomination becomes increasingly in peril. The reason: Many Democrats are alarmed at the divisive GOP primary contest and are worried that strong-arming Sanders will prompt a similar chaotic result on their side of the aisle.
Moreover, they believe, Sanders' attacks on Clinton have been relatively mild, so they are content with him staying in the race as long as he's willing to campaign -- at least for now.
"It's been positive for Hillary," Sen. Barbara Boxer, the California Democrat and early Clinton supporter, said of Sanders' presence in the race. "Bernie's issue are important. The way I look at it, unlike the presidential (campaign) on the Republican side, I don't see Bernie as a negative."
Yet Sanders' continued candidacy presents a risk for Clinton, who is struggling to energize the Democratic base, particularly younger and more progressive voters. The longer Sanders stays in the race, the harder it would be to focus on the general election -- a problem that grows much dicier if Donald Trump starts to run away with the GOP nomination.
But speaking to reporters Tuesday, Senate Minority Leader Harry Reid said he had no qualms with Sanders battling it out until the summer. "I'm satisfied with how the primary is moving along," Reid said.
Sanders, who raised $40 million in February alone, appears likely to have the resources to continue battling Clinton for as long as he wants to remain in the race, even if Clinton starts to pull away. The hope for Democrats is that Clinton piles up an insurmountable delegate lead -- and Sanders decides on his own it's time to call it quits, without any intervention from the party establishment.
But unlike the GOP race, where the party is growing increasingly divided about the prospects of fighting it on the convention floor, Democrats say they have no problem with it.
"He has said he's going to continue to the convention, and I take him at his word -- and certainly is entitled to do that," said Sen. Richard Blumenthal, D-Connecticut. "There's nothing lost by his continuing."
Still, Sanders has increasingly attacked Clinton for her reversal on key issues -- ranging from trade to the Iraq war -- and has accused her of being too close to Wall Street. Yet some Democrats hope that if Sanders continues a long campaign, he will avoid getting into a bitter and personal fight with Clinton.
But New York Sen. Chuck Schumer, the No. 3 Democrat, said the fight is nothing in comparison to the vitriol on the GOP side, where Trump and his rivals have engaged in a daily tit-for-tat of mudslinging.
"Our primary is on the merits," Schumer said Tuesday. "People are discussing issues, not calling names at each other."
Senate Minority Whip Dick Durbin, D-Illinois, added: "(Sanders) has waged an amazing campaign. He has a huge reservoir of support across this country and in my state. As long as he is a viable candidate, he'll continue in this race."
Asked if his opinion would change if Sanders were no longer viable, Durbin smiled, calling it "speculation." He walked into a party lunch, declining to comment further.