"If the president of the United States insists on submitting a nominee under these circumstances, Senator Biden...knows what the Senate should do," Grassley said. "And, I believe, in his heart of hearts, he understands why it must."
He suggested that senators would at least privately have the vice president's understanding because of the "Biden Rules," though he said he expects Biden to publicly back Obama's nominee.
Under the rules, according to Grassley, during a presidential election year the president should consider refraining from naming a Supreme Court nominee until after the election, and the Judiciary Committee should seriously consider not giving hearings until after the election.
Grassley's remarks come after a video circulated online Monday of Biden giving a speech on the Senate floor in 1992. Then a senator he said that then-President George H.W. Bush should wait until after the election to fill a hypothetical vacant Supreme Court seat.
Grassley is at the center of a battle over whether or not to fill Justice Antonin Scalia's seat during Obama's final year, with the Iowa Republican telling reporters last week that he hasn't made a decision on if the nominee will get a hearing.
Republicans argue that the decision should be taken out of the partisan environment of the presidential election, and Obama's successor should fill the seat.
Democrats, however, say that Republicans are shirking their constitutional duties.
Senate Minority Leader Harry ReidHarry Mason ReidDemocrats say change to filibuster just a matter of time The Hill's 12:30 Report - Presented by Connected Commerce Council - Biden faces reporters as his agenda teeters Biden hits one-year mark in dire straits MORE (D-Nev.) doubled down on that Monday, suggesting Republicans were "holding hostage an entire branch of government."
"This is a foolish gambit," he added. "A full blown effort to delegitimize President Obama."