It seems Riggleman had been whining about this issue all season, even enlisting the aid of reporters to lobby for him.
Rizzo, the GM, had rushed home last month canceling a scouting trip, to, in his words, put out fires in the club house..I recall this now that he mentioned it which occured after Riggleman pulled Marquis out of a game, causing a huge public screaming match by Marquis with Riggleman which went on for an extended time period publicly and privately with Riggleman chasing Marquis around the clubhouse screaming.."do you want a part of me" for several minutes.
I dont think Rizzo thinks Riggleman is very good in the clubhouse but my issue is what Rigglemans' perception of his job is. He seemed to feel he was slighted by his low salary($600,000) and lack of commitment by management in not offering or discussing with him a longterm deal. Well current GM Rizzo had the same deal not so long ago and was told, in essence, produce and it'll happen. He did and got a 5 year deal. There was a message there for Riggleman which he failed to understand or think applied to him..see his remark about being 58 and lack of respect..
There is a reason he hadnt managed in 10 years which was borne out sadly again yesterday.
He just doesnt get the relationship between management and employee and completing the job he was hired to do.
I liked Riggleman a lot but after learning this think we need someone else.

Jim Riggleman resigned yesterday after the Natnals beat Seattle 1-0. Riggleman had approached General Manager Mike Rizzo and asked the team to pick up his option for 2012. When Rizzzo replied that he wasn't ready to discuss it at this time, Riggleman packed his bags. Riggleman had been working on 1-year contracts since replacing Manny Acta in 2009, at a salary of $600,000 per year. Washington is 38-37, the first time they've been above .500 this late in the season since 2005. They have also won 15 of the last 21 and 11 of the last 12. In my humble, unlearned opinion, letting Riggleman walk was a major mistake. The Natnals are relevant for the first time in recent memory and,  with Bryce Harper and Stephen Strasburg among their good young players, have a bright future.

Interesting. I wasn't aware of all of the other issues until I read your post. Guess there was a reason why Rizzo wasn't ready to discuss his option yet. Thanks for pointing that out.

Yes, at a game over 500, the Washington Nationals (for them) are playing very good baseball. They do have a young star in Ryan Zimmerman and some other young player,  Wilton Ramos, Jordan Zimmerman, and Drew Storen to build around. And as you mentioned, Stephen Strasburg will hopefully be back and return to his dominant form prior to his injury. Bryce Harper is prob. a year or two away.

But let's not confuse Jim Riggleman with the all time great managers. His career record is 662-824 and in 12 seasons, his best finish was guiding the Cubs to second place in 1998. While he had the Nationals competitive this season, I agree with the GM for not caving in to his immediate demands for a contract extension. Why should he have picked up his option on the spot? Since when is a .500 record (not even 1/2 way through the season no less) something to celebrate? The Nationals could just as easily go into a tail spin the rest of the way and finish with 70 wins. Wait until the end of the season to determine Riggleman's fate. His track record indicates that he has been a mediocre manager at best and as such, easily replaceable. The Nationals front office did the right thing. Riggleman should have stayed, and if the Nationals continued to play well his option would have been picked up. But asked to make a decision today about his future, they had no choice but to let him walk.

Davey Johnson will run the team for the rest of this season and next season.

And I will guess he will be hard pressed to find another major position in the MLB.