IMHO, people prefer "trust, but check" over "blind trust". You can cast a referendum, if you are unsure. Hitler was elected in a democratic way, so it's possible that your democratic ally can turn into a totalitarian enemy at a next election.

Also, it is easier to check for Russian spies in a government from outside, than from inside. For example, soviet agent in Germany government, called "D-104" in memories of Yurii Drozdov, is still not found. I suspect Schröder, which works for Russian Gasprom now, but he may leave a replacement agent, to work after him. (Merkel?)