Over the years, I have found that when the Congress works late into December, it can often bring out the worst in lawmakers, as late nights, frayed nerves, longstanding personal or political disputes and legislative gridlock can result in feelings that are not exactly conducive to handshakes, hugs, smiles and good holiday tidings.

And that is where the U.S. Senate is right now.

"Congress is finishing this year less popular than a cockroach, and mindless, knee-jerk obstruction from Republicans is exactly why," said Senate Majority Leader Harry Reid.

Not to be outdone, Republicans responded in kind on Thursday.

"We're getting sick and tired of the dictatorial way that the United States Senate is being run," thundered Sen. John McCain (R-AZ), as he and other GOP Senators took direct aim at Reid on the Senate floor.

"I'm appalled," said Sen. Orrin Hatch (R-UT), as Republicans continue to protest the "nuclear option" changes made last month by Democrats to water down rules on the filibuster.

In order to showcase their displeasure with the filibuster rules change, Republicans have been forcing Democrats in the Senate to jump over every legislative hurdle and through every procedural hoop possible, stretching out the work of the last two weeks.

Last week, Republicans kept the Senate in session for over 48 straight hours at one point, and instead of letting everyone go home for the holidays early, the dispute threatened to keep the Senate working well into the weekend on a series of nominations.

"With all the Republican obstruction and delay we've seen over the last two weeks, is it any wonder that Democrats changed the rules last month?" Senate Majority Leader Harry Reid asked rhetorically on the Senate floor.

"Of course not," Reid said, as he rapped the GOP for what he labeled a Republican "bad habit" of favoring delaying tactics; his spokesman labeled the GOP floor delay a "tantrum."

While Democrats blasted the GOP for delaying nominations, Republicans complained about how Democrats were blocking the GOP from offering any amendments on bills.

"We haven't debated NSA, we haven't debated the issue of sexual assault," McCain complained about the lack of amendments and votes on a major defense policy bill.

"The process was terrible," said Sen. Jim Inhofe (R-OK), the top Republican on the Senate Armed Services Committee, said of the defense bill, which was finally approved just before midnight on Thursday night.

"The senate has not been functioning like it should for some time," said Sen. Charles Grassley (R-IA).

Republicans argue Sen. Reid has blocked amendments 79 times this year on the Senate floor, using a special procedural move, known as "filling the tree."

Democrats scoffed at such charges; Sen. Jeff Merkley (D-OR) said it was Republicans who were guilty of "paralyzing strategies" on the Senate floor, as he said GOP arguments were "extraordinarily misleading."

The dispute led to a late night for Senators on Thursday, as they filed into the chamber for votes well after 11 pm, but the threats of working through the weekend evaporated, as a deal was worked out to let Senators go home by midday on Friday.

"Greateful to leadership for vote schedule deal avoiding overnight session, since I had the 1-4 am shift in the chair," said Sen. Chris Murphy (D-CT).

"Saner heads have prevailed," said Sen. Dan Coats (R-IN), as the Senate pulled back from the possibility of more all-night sessions - though Coats then launched into an attack on Democrats for employing the 'nuclear option' and "filling the tree" to block amendments.

"What are you afraid of?  A vote?" Coats asked, expressing the frustration of GOP Senators.  "You're stiffing us," Coats said to Democrats.

When Senators return on January 6, one of their first orders of business will be to approve the nomination of Janet Yellen to head the Federal Reserve.   They will join to easily approve her nomination.

After that vote though, the Senate may be back in the same place - with more bickering over "filling the tree" and filibusters.

It's like the chicken and the egg, as both sides say the other is to blame.