If Sanders keeps up his fundraising prowess and eventually drops out, it would put him in a relatively unique position: defeated but with a cash surplus.
So what could he do with the remaining money?
The Federal Election Commission outlines multiple possible uses for a campaign committee's surplus cash. It can become a multicandidate committee and use the money within the rules of those organizations.
Sanders' cash could go to national, state or local party committees or to other candidates. It could also be donated to charitable organizations or state and local candidates, within certain limits.
After clearing some regulatory hurdles, Sanders could also channel it to a possible Senate re-election bid in 2018, said Larry Noble, general counsel at the Campaign Legal Center. The committee would also have the option to return cash to donors, possibly on a prorated basis based on the size of contributions, he added.
Still, Noble noted Sanders "doesn't have any obligation to wind down" his campaign at this point.
Sanders' next test comes Tuesday with the Indiana primary. An average of recent polls shows Clinton with a four-point lead in the state, according to RealClearPolitics.