Blockchain technology has so many uses outside Bitcoin and digital currency. A blockchain is basically a shared ledger of data. Importantly this ledger is tamper proof. Once data has been recorded it can't be removed or altered without consensus of the whole system. So there is no single point of failure like in a centralised system.

If a government were to implement Blockchain technology in elections. It wouldn't have all the features of a decentralised blockchain. It would be a private network where the government hold an authority to determine members and functions of each member. It can decide which members can participate in the network. It would select who would maintain shared copies of the ledger. And the government would have the ability to edit entries on the blockchain.
But it maintains the concept of immutability and consensus making an external attack on the system difficult.

So in short, Blockchain can very well be used in elections, but it wouldn't employ the same principles as bitcoin does. It would still be centralised and there would still be avenues for corruption.