"The changes we’re making are very, very minimal. What we’re doing is saying, ‘Look, American people, shouldn’t President Obama have somebody working for him that he wants?’" Mr. Reid said on NBC’s "Meet the Press" program as he defended the "nuclear option" to change the rules.
Under that scenario, Mr. Reid would use the Democrats’ majority in the chamber to overturn decades of precedent — which amounts to a rules change when it comes to parliamentary procedure — and establish that nonjudicial nominees are not debatable to the same degree as bills.
Mr. Reid’s Republican counterpart, Sen. Mitch McConnell of Kentucky, said Democrats are itching for a fight when there isn’t one to be had.
He said Senate Republicans have confirmed Mr. Obama’s picks at a faster rate than President George W. Bush was getting at the same point during his time in office, and that Republicans haven’t defeated any of the president’s major executive nominees.
"When it comes to nominations, as I’ve indicated, the president hasn’t lost anybody — he hasn’t lost anybody," said Mr. McConnell, also appearing on NBC. "Are they saying they don’t want us to even debate these nominations?"
In a sign of how tense the fight has become, the two leaders did not appear on the same panel with each other, but spoke sequentially to moderator David Gregory.
Mr. Reid has set up seven potential filibuster votes for Tuesday morning: the nominations for Labor Department secretary, Environmental Protection Agency administrator, three members of the National Labor Relations Board, president of the Export-Import Bank, and director of the Consumer Financial Protection Bureau.
The question is whether Mr. Reid would force a rules change if Republicans filibuster only some of these nominees.
He has scheduled the three most controversial votes — the CFPB and two of the NLRB picks — to be first, which means he appears to be trying to make Republicans cave.
Mr. McConnell said Republicans would allow most of the nominees, including those to whom they strongly object, such as Thomas E. Perez, the Labor secretary pick.
But the three main fights over the NLRB and CFPB nominees are trickier. When those three were facing potential Republican blockades early last year, Mr. Obama used his recess appointment powers to name them to their jobs — but he acted at a time when the Senate didn’t consider itself in recess.
A federal appeals court has ruled that Mr. Obama exceeded his bounds with the NLRB appointment and invalidated one of the board’s rulings, calling the rest into question. The Supreme Court last month said it would take the case.
Republicans argue that Mr. Reid is risking major damage to the institution of the Senate in order to rescue the NLRB from its precarious position.
At an all-senators meeting Monday morning, Republicans hope they can talk the majority out of pressing ahead.
Ahead of the showdown, each side deployed numbers to argue its case.
Republicans said they have confirmed an exceptional number of Mr. Obama’s nominees, including every executive branch appointment that has come to the Senate floor. They say they have obstructed only a few judges who were outside of mainstream legal thought.
Democrats say Republicans have pushed obstruction behind closed doors by slow-walking nominees in committees, demanding answers to hundreds of questions about their histories and policy positions.
Mr. Reid said Republicans usually don’t even object to the nominees, but rather are using them to attack the president’s policies or the role of government itself.
"They have nothing against the qualifications. They don’t like the jobs these people have," Mr. Reid said.
The filibuster is not part of Senate rules. It’s a term that is applied when a single senator or group of senators wants to hold an indefinite debate on an issue.
Some issues and motions, such as bringing a budget to the Senate floor, are considered nondebatable and cannot be filibustered, but most of the regular motions are debatable. It takes 60 votes to cut off debate. When that vote fails, it is considered a filibuster.