Long-simmering divisions among Republicans burst into public view Tuesday evening, when GOP moderates challenged tea-party conservatives on the Senate floor over their refusal to proceed to formal negotiations with Democrats over the federal budget.

On one side, Sens. Rand Paul (R-Ky.) and Ted Cruz (R-Tex.) insisted that the GOP must block any effort to name a conference committee to reconcile differences between the budgets approved by the Democrat-controlled Senate, which proposes nearly $1 trillion in new taxes over the next decade, and the Republican House, which proposes to eliminate the deficit within 10 years entirely through spending cuts.

Their reason: Democrats can’t be trusted not to sneak in an automatic increase in the federal debt limit.

“This fight right now is the fight over the debt ceiling, because what it would mean if we go to a conference committee is that as sure as night follows day, we would find ourselves in a month or two with a debt ceiling increase coming back ... with no conditions whatsoever,” Cruz said.

On the other side, Sens. John McCain (R-Ariz.) and Susan Collins (R-Maine.) questioned that argument, noting that Democrats couldn’t do anything in conference without the approval of the House — which, McCain said, “happens to be a majority of our party.”

The battle over the 2014 budget

“So we don’t trust the majority party on the other side of the [Capitol] to come to conference and not hold to the fiscal discipline that we want to see happen? Isn’t that a little bit bizarre?” McCain said.

McCain and Collins also argued that the stall tactics look ridiculous after months of GOP complaints about the refusal by Senate Democrats to adopt a budget. The first Senate budget in three years won approval 59 days ago, and Republicans have been dragging their feet every since.

“What are we on my side of the aisle doing?” demanded McCain.

“We have called repeatedly for a return to regular order in this body,” added Collins. “Well, regular order is going to conference.”

Democrats were quietly gleeful about the public spat, which has been brewing for days. Many Senate Republican privately complain that Senate GOP leaders are protecting the House GOP, which could face a series of uncomfortable votes if a conference committee is named and fails to quickly reach a resolution.

No one expects budget negotiations to go smoothly. House Budget Committee Chairman Paul Ryan (R-Wis.) has said he views the debt limit deadline as critical to forcing an agreement. But that deadline has now been pushed to well after Labor Day.

In recent conversations with reporters, Collins has called the stall tactics “absurd;” McCain called them “insane” and “incomprehensible.” As their frustrations played out on the Senate floor Tuesday evening, aides to Senate Majority Leader Harry Reid (D-Nev.) issued a press release titled “GOP divisions erupt over budget.”

Meanwhile, Sen. Barbara Boxer (D-Calif.) entered the fray to offer her conservative colleagues a lesson in the ways of representative democracy.

“The Republicans, except for Senator McCain and Senator Collins..., are stopping us, this nation, from having a budget, and they’re saying their reason is something might happen in the conference,” Boxer said. “Well, that is not the way we work in a democracy. Anything can happen any moment.

“Paul Ryan has a budget that I think is apocalyptic that you may well support. [Senate Budget Committee Chairman] Patty Murray [D-Wash.] has a budget that you probably think is apocalyptic,” Boxer continued. “They’re going to get into that conference and they’re going to work together. That’s called democracy.”