I believe Belarussian suffered the most due to the Soviets and now due to Lukashenko. If you look at Lukashenko's (the president of Belarus') website, you can view it in Russian or English, but not Belarussian.
The official site of the goverment of Belarus' is in Russian only.
I believe after the break-up of the Soviet union there was an initial surge in Belarussian language, but Lukashenko and his government have supressed and reversed it.
P.s. did you know that Minsk is Mensk in Belarussian?