The focus of the Senate Banking Committee's inquiry has been forward-looking, seeking to identify steps that can be taken to prevent such situations from occurring in the future. The task of investigating potential wrongdoing and the disappearance of funds has primarily been taken up by other congressional panels, notably the House Financial Services Committee.

"People rightly find it inexplicable that there are no answers," Kyrillos told The Hill, adding that the Senate has a responsibility to get to the bottom of where the money went. "If you can't be objective and there isn't the confidence that you can roll up your sleeves and dig out the facts, seems to me it makes sense to step aside."

In the hearing, Menendez questioned James Giddens and two other MF Global trustee for about ten minutes about the factors that led to the firm's demise, the state of the investigation and the prospects for the funds to be recovered, but didn't question the trustee's about Corzine's role in the disappearance of customer money.

"This is a pretty hypocritical attack coming from Republican Joe Kyrillos who has defended Wall Street and millionaires at just about every opportunity," said Michael Soliman, Menendez's campaign manager. "Sen. Bob MenendezRobert (Bob) MenendezThe Hill's Morning Report: Can Trump close the deal with North Korea? Senate must save itself by confirming Mike Pompeo Poll: Menendez has 17-point lead over GOP challenger MORE has been a leader in fighting back for the middle class against the excesses of Wall Street and big banks."

Soliman added that Kyrillos had "sided with giant corporations to deny health care to people with pre-existing conditions" and refuses to make millionaires pay their fair share.

- This post was updated on May 4 at 5:33 p.m.