The relevant question to ask here is: Why? After all, the past two Congresses were renowned largely for their historic lack of productivity.

With Republicans reclaiming the Senate majority and widening their majority in the House in the 2014 election, there seemed little likelihood that the period between January 2014 and November 2016 would be markedly different from the four years that had preceded it.

And yet, here we are.

Billy Moore, a longtime Democratic congressional staffer and now a lobbyist, sought to explain the detente in a weekly newsletter he sends to Washington types. He wrote:

Congress continued to build bipartisan momentum in the first week of the April session, clearing the permanent Medicare physician pay reform measure for President Barack Obama's signature, confirming a federal judge and beginning a budget resolution conference that could continue the momentum into the summer. . . . The most important factors these initiatives have in common is a consensus on the role of government and committee leadership that want to work together to get things done. Where an issue lacks consensus on government's role, such as immigration, health care or environmental protection, Washington still appears stymied.

I also asked a handful of longtime Republican congressional hands to explain the sudden unfreezing. The name that kept coming up in those conversations was Sen. Harry Reid (D-Nev.).

"I think there was a significant pent-up desire on both sides to return to legislating," said Billy Piper, a former top aide to Sen. Mitch McConnell and now a GOP lobbyist. "These guys don't work so hard to win elections to just come up here and be potted plants. They want to accomplish things, and the last several years they have been prevented by Leader Reid from even trying."

Added another smart Republican mind: "Following the collapse of the Grand Bargain talks in the summer of 2011, Reid essentially shut down the Senate (presumably at President Obama’s request) until after the presidential election. . . . Now, McConnell is making the Senate work again, and President Obama (in the final quarter of his presidency) would like some sort of second-term legacy. So things are moving."

It's not just Republicans who are blaming Reid. Sen. Joe Manchin (D-W.Va.), who announced this week that he will seek reelection in 2016 rather than run for governor, took a shot at Reid's tenure as leader, too. “His leadership and the things he thought would work did not," Manchin said on "Morning Joe." "So with that, you just move on.”

For the record, not all Democrats -- or even most -- blame Reid. Democrats generally insist that the reason things have begun to work better is because their side isn't willing to block legislation the same way Republicans did when they served in the Senate minority.

My sense is that it's a combination of these factors. Yes, it is true that McConnell has opened up the amendment process in the Senate, allowing more voices to be heard and members -- Republicans and Democrats -- to feel as though they are a bigger part of the process. But, it is also true that McConnell (and House Speaker John Boehner) believe deeply in the need to demonstrate a capacity to govern as opposed to simply stand in opposition in advance of the 2016 election. And, Obama is, without question, in search of major and minor second-term accomplishments.

Add it up and you get the rarest of things: a genuine interest on both sides of Pennsylvania Avenue to work together. As Moore notes, this kumbaya moment isn't likely to extend to pricklier fights on such issues as immigration or health care. Those bigger-ticket battles will continue to be largely litigated at the legal level and on the 2016 campaign trail.

But that's for another day. Today we celebrate a political process that is moving. Finally.