Many theories are abound for the under performance of the Nationals and Orioles this year but let’s get to the root causes.
Nationals: The local papers keep listing these guys as “in the race” for the second National League wild-card spot but you can take out that garbage; these guys are done. The fans of the preseason favorite to win the World Series, and possessor of starting pitching dominance, and resident in one of the weakest divisions in baseball, have overlooked one critical factor that has lead to their downfall; Davey Johnson is a lame duck. 
Just as lame duck presidents struggle to build consensus and lead the nation in the final years of a second term presidency, ball clubs are aware when their manager is not returning, and don’t play as hard or with the focus required to exhibit excellence over the course of a long season. Employees of an organization have got to feel a commitment to success in the short term, and know that a long-term business strategy exists as well. Johnson’s temporary status has subconsciously torpedoed the long term plan, and the Nats have gotten by on .500-level concentration and effort. Their record reflects the inputs.
Orioles:
Baseball is a game of statistics and averages and this O’s team is too mediocre in too many critical areas. While they are not mathematically eliminated from the race, all the probabilities are against them. They play in the most competitive division in baseball, their starting pitching is inconsistent and incapable of getting the team late into games, and while their offense is loaded with power, they’ve become too reliant on the home run. I like their mental approach of taking games one at time and not confusing short term wins and losses with long term objectives, but the inputs are averaging out and taking their toll. 
Buck Showalter is no dummy and said as much about a month ago when he indicated that starting pitching was the key to a post-season appearance. The O’s don’t have it and their opponents do; enough said.
With memories of 14 consecutive losing seasons still too fresh in my mind, I’m willing to get by on a 85-win campaign and relish the thought of last year’s magical finish a little longer, but the organization will need to make a concerted effort to improve their starting staff for next year because competition in the AL East never let’s up.
All About DC Sports 
I can’t speak to the Orioles, but I find the notion of Davey’s lame-duck status playing a role to be a troubling one. It’s Rizzo, more than Davey, who determines the future of the Nats players, and I can’t believe they not doing their best to impress him. Plus I think they like Davey so much, the fact that they wanted to win it for him was an offsetting factor. I think the Nats’ problem is that they’re just not so good (yet). I love Harper, but he’s not as good as the hype (yet). Same for Strasburg, Rendone and the other young players. The vets (Zim, especially) had a weaker than normal season. LaRoche had his worst season in a while, and Span and Haren took too long to get going. Only Worth, Desmond, and Jordan Zimmermann performed to expectations. But who really knows? Interesting and thought-provoking post, though.
Mark, so was last year an outlier for the Nats or is this year? Maybe they are somewhere in between. Thanks for the comment.