TRENTON -- Technically, 913 delegates are still up for grabs in Democratic primaries to be held in hugely populous states like New Jersey and California next month.

But U.S. Sen. Bernie Sanders of Vermont is confronting a hard political truth: His rival, former Secretary of State Hillary Clinton is now 97 percent of the way toward securing the Democratic nomination for president. She currently has 2,310 of the needed 2,383 delegates to become their party's nominee for president.

When NJ Advance Media asked senior Clinton campaign operatives how much longer Sanders should stay in the race, they answered politely and politically: "As long as he feels he needs to."

Of course, with more than 9 million Democrats having voted for the underdog populist, the Clinton camp can ill afford to alienate his supporters.

But with Donald Trump having clinched the Republican nomination for president by reaching the 1,237 threshold last week, every day that goes by without Clinton focusing her attacks on her GOP rival is politically risky.

Even Sanders' colleagues in the U.S. Senate are getting worried. U.S. Sen. Dianne Feinstein (D-Calif.) told the Associated Press that Sanders is damaging her party's chances against Trump come November. U.S. Sen. Sherrod Brown (D-Ohio) has said Sanders's refusal to exit the race "sort of slows the takeoff of (Clinton's) general-election campaign."

Much of the reason for Sanders' reluctance to take his ball and go home is the still-lingering, if unlikely, chance that Clinton's private email server scandal could result in a politically devastating indictment, demolishing her chances of winning in a general election.

What do you think is the right thing for Sanders to do? Vote in our informal, unscientific poll below.

Claude Brodesser-Akner may be reached at cbrodesser@njadvancemedia.com. Follow him on Twitter @ClaudeBrodesser. Find NJ.com Politics on Facebook.