But he said Moldova appears to be bucking that trend, with signs mounting that its parliamentary elections on 6 March might not prove to be free and fair.
"We hear reports that are disturbing about repression of the [Moldovan] opposition, about failure to allow demonstrations and gatherings," said McCain, who has co-sponsored a resolution in the Senate calling for fairness and transparency in Moldova's elections.
The senator expressed hope that Russian President Vladimir Putin would take a different approach to Moldova's elections than the stance he adopted toward Ukraine's presidential polls last year.
But McCain added: "I fear that President Putin has not learned the lesson of Ukraine and his desire to hold the line against further democratic gains near his border may have even increased."
Putin backed former Prime Minister Viktor Yanukovych in Ukraine's polls, which were initially deemed fraudulent by the West and Ukraine's Supreme Court.
But Yanukovych was defeated after opposition candidate Viktor Yushchenko rode a wave of massive popular support to victory in a re-vote in December.
Moldova's Communist President Vladimir Voronin, once an ally of Russia, now seeks closer ties to Europe as relations with Moscow have cooled. Moldova accuses Russia of assisting Russian-speaking separatists in its Transdniestr region.