DORGAN STUNS SENATE, ANNOUNCES RETIREMENT…. As you may have heard, there were quite a few election-related developments overnight. Let’s start with the biggest, and arguably most consequential, surprise.

North Dakota Democratic Sen. Byron Dorgan will not run for re-election later this year, creating a major pickup opportunity for Republicans.

“After a lot of thought I have made the very difficult decision that I will not be seeking reelection in 2010,” Dorgan wrote in a memo to staff distributed this afternoon. “This decision is not a reflection of any dissatisfaction with my work in the Senate, nor is it connected to a potential election contest next fall (frankly, I believe if I were to run for another term I would be reelected).”

Dorgan was facing a potentially serious re-election race against Gov. John Hoeven (R) in November. He was first elected to the Senate in 1992 and, despite the clear GOP lean of the state, hadn’t faced a serious re-election challenge since then.

No one saw this coming, and there’d been no rumors about Dorgan even considering retirement. Indeed, while Hoeven’s interest sparked some murmuring, the incumbent senator was, before yesterday, positioned to possibly run unopposed.

Dorgan’s departure creates a very strong pick-up opportunity for Republicans. Among Democrats, the most appealing candidate would likely be Rep. Earl Pomeroy, North Dakota’s at-large representative, who has not yet signaled his intentions. In the meantime, Hoeven, a popular three-term governor, is reportedly preparing to run for the now-open Senate seat, and would be heavily favored to win, no matter who his opponent might be.

Regardless, Dorgan will leave an impressive legacy after 18 years in the Senate, serving as something of a populist champion and hero of the middle class throughout his career. In fact, we here at the Monthly have grown especially fond of Dorgan over the years — just two years into his first term, he wrote an important cover story for us on financial deregulation and the dangers of derivatives. He was right, but his prescient warnings were largely ignored, and we’re still paying the price. What’s more in October, Dorgan appeared at an event co-sponsored by the Monthly to discuss the renewed efforts at re-regulation.

The Senate won’t be the same, and won’t be as strong, without him.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.