Sen. Robert MenendezRobert (Bob) MenendezJustice Dept intends to re-try Menendez in corruption case DACA is neither bipartisan nor in America's interest Senate DACA deal picks up GOP supporters MORE (D-N.J.) invoked the words of Rev. Martin Luther King Jr. during a speech Sunday, as he denied allegations that he improperly aided a political donor.

"Dr. King said that ‘the arc of the moral universe is long, but it bends toward justice,’ " Menendez said according to the Newark-based Star-Ledger, during a speech at the Shiloh Baptist Church in Trenton, N.J. "In the end, I believe that justice will overcome the forces of darkness. Scriptures — scriptures tell us that he who 'puts his hand to the plough and looks back is not fit for the Kingdom of God.'

"I have my hand on the plough and I am going to continue to look forward and to work to make that plough lead us to the fulfillment of educational, economic and healthcare opportunity in this country," Menendez added.

Menendez has maintained his innocence against allegations that he improperly helped Dr. Salomon Melgen, a campaign donor who took the senator on private trips to the Dominican Republic.

Menendez is accused of interceding on Melgen’s behalf in a Medicare overbilling dispute and of pressing federal officials to enforce a port-security contract that would have benefited a firm owned by Melgen.

Recently, Menendez admitted that he had taken previously undisclosed trips on a private jet owned by Melgen, reimbursing him $60,000 for the gifts.

A report in The Washington Post has said that FBI agents are also investigating whether Menendez and Melgen consorted with prostitutes during their trips to the Dominican Republican. The prostitution claims were first alleged by the conservative website The Daily Caller.

Menendez has denied those accusations and said he is the victim of "faceless, nameless individuals from right-wing sources" who are trying to "destroy a lifetime of work."

But the allegations appear to have taken a toll politically.

A recent Quinnipiac University poll found Menendez's approval had dropped sharply among New Jersey voters. The poll found that 41 percent of New Jersey voters disapprove of Menendez's job performance while 36 percent approve. A month earlier 51 percent said they approved of the job Menendez is doing while 33 said they disapproved.

The junior senator dismissed those poll numbers on Sunday.

"The only poll that matters is what do I get accomplished each and every day," Menendez said.