It's certainly an interesting collocation, but the meaning is different here (many political bosses and even lesser politicians only become rich AFTER being elected...).
http://www.oxforddictionaries.com/definition/english/robber-...a ruthless and unscrupulous plutocrat.
More example sentences
Henry Huttleston Rogers, a well-known robber baron who made millions as a vice president of Standard Oil, bought Atlas Tack and brought it to Fairhaven in 1901.
[plutocrat = a person whose power derives from their wealth]