constant, evidence-based accusations of widespread electoral fraud
There are conflicting views on that.
Accusations of fraud are mostly aboutRussian parliament elections of 2011. Pro-Putin party was accused of fraud in many districts, which I personally think is correct. (But, strangely enough, Israeli foreign minister, has found those elections fair and democratic... http://www.haaretz.com/news/diplomacy-defense/lieberman-russ...)
On the other hand, most definetely Putin did not need any fraud to help him win presidential elections in 2012. He had an overwhelming support among common Russians. Forecasts by anti-Putin polling organisation Levada Centre promised him 63% of the vote (http://en.wikipedia.org/wiki/Russian_presidential_election,_...), and he indeed got 63.5%. His closest competitor (a communist) got 17%.
To win elections fraudulently, Putin had to doctor close to half of the bulletins, which seems unlikely, given worldwide scrutiny of the election, and his own efforts to dispel doubts such as installing live webcams at every polling station etc.
Tl;dr Putin won because he is popular, not because of the fraud.
