Democrats have complained about Republican attempts to block some of President Obama’s nominees. Harkin said some nominees are being held up not because they’re unqualified but because Republicans dislike the agencies the person would lead, such as the National Labor Relations Board (NLRB), Consumer Financial Protection Bureau (CFPB) and Environmental Protection Agency (EPA).

“A single senator some times can hold up a nominee not because the nominee isn’t qualified but because they want to change something else,” Harkin said. “They don’t like the National Labor Relations Board so what do they do? They can’t repeal it, so they make it inoperable.”

Senate Majority Leader Harry ReidHarry Mason ReidMcConnell not yet ready to change rules for Trump nominees The Hill's Morning Report — Sponsored by CVS Health — Trump’s love-hate relationship with the Senate Trump to press GOP on changing Senate rules MORE (D-Nev.) has threatened to use the “nuclear option” — changing the Senate rules with a simple-majority vote — in order to thwart Republican obstruction on seven of Obama’s nominees. 

Later Monday, the Senate will hold a closed-door joint caucus to discuss the pros and cons of changing the rules. Democrats have argued that the president should be able to select his own team and that executive branch nominees shouldn’t be held to a 60-vote threshold.

Harkin predicted that a deal could be reached to avoid using the nuclear option but he said he would not support any deal unless it got “rid of the filibuster on the executive branch.”

“I hope the only deal we reach is that any president should have the right to put his or her team in place,” Harkin said. “That is the only deal that will get us out of this track we find ourselves in.”

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeOvernight Energy: Reporters barred from Day 2 of EPA summit | Dems blame Trump for gas price increases | Massachusetts to get new offshore wind farm Jeff Flake: Trump has 'debased' the presidency Senate Democrats look for traction on gas prices MORE (R-Ariz.) countered that what Harkin and other Democrats are calling for is “hazardous” and will have “unforeseen consequences.”

“The rule change being sought this week is more far reaching than it’s being advertised,” Flake said. “It is hazardous and will have unforeseen consequences.”

Flake and Republicans have argued that they are simply exercising the rights in the Constitution for the Senate to “advise and consent” on executive nominees and that changing the rules would harm minority rights in the Senate.

Nominees Democrats are hoping to vote for this week are Richard Cordray to be Director of the Bureau of Consumer Financial Protection; Richard Griffin, Sharon Block and Mark Pearce to the National Labor Relations Board; Fred Hochberg to be President of the Export-Import Bank; Thomas PerezThomas Edward PerezClinton’s top five vice presidential picks Government social programs: Triumph of hope over evidence Labor’s 'wasteful spending and mismanagement” at Workers’ Comp MORE to be Secretary of Labor; and Gina McCarthyRegina (Gina) McCarthyPruitt granted extension to file financial disclosure form Pruitt's 24/7 security requested over fears of Trump policy backlash EPA documents detail threats against Pruitt MORE to be Administrator of the Environmental Protection Agency.