Well, no. He's not close to the absolute worst ever. There have been an awful lot of totally unprepared dogs among MLB's GMs over the years, and the very fact of Bowden's longevity as a GM for 15 years is evidence that he isn't that bad. But looking at the men who have held the post of major league general manager for as long as Bowden has, one could argue that he's almost the absolute worst of the last 58 years.
Since 1950, based on the Baseball America executive database and compilations at BaseballCube.com, 23 men have served as GMs in Major League Baseball for as long as Bowden's 15 years. Of that group, only three have lower winning percentages than Bowden's current lifetime .483: former Marlins and current Tigers GM Dave Dombrowski (.454), 1957-1975 Cubs' GM John Holland (.466), and, interestingly, Calvin Griffith (.480).
Griffith of course is the hated former Senators' GM, owner, and racist, who inherited the team from his uncle and promptly moved the team to Minnesota because, he later joked, "Black people don't go to ball games, but they'll fill up a rassling ring and put up such a chant they'll scare you to death," he said. "We came (to Minnesota) because you've got good, hard-working white people here."
Not long ago, it looked pretty likely that Bowden would sink below Griffith this season. However it now seems very unlikely that the Nationals will lose the 104 games that would be needed to drive Bowden's career winning percentage to .479. If Bowden's not fired this off season, however, I would put the over-under at about May 20 for him to sink below the Griffith Line.
And although Dombrowski has lost a higher percentage of his games than Bowden has, he's also done something that Bowden has never come close to doing: win a World Series. Dombrowski's Marlins won it all in 1997. Likewise, Griffith's Twins made the World Series once, losing to the Dodgers in 1969. And a Twins team almost completely built by Griffith won the World Series in 1987, three years after Griffith retired.
Only the Cubs' John Holland, who never made the playoffs even once, posting just seven winning seasons out of 19, clearly in every way exceeds Bowden's record of relentless failure.