I once got a call from the campaign of some local candidate running for MP or MPP. Can't remember which. Anyway, this campaign volunteer asks me who I'm voting for. I tell him it's none of his business, but if he really must know, I was voting for his guy. But being as his campaign is the only one currently abusing my telephone number, I'm seriously reconsidering. He got flustered and started to make the usual excuses, and I hung up.
At least it was a human. I don't know if you get what we in the US call "robo-calls", calls by a machine that just deliver a recorded message.
A couple of years ago, a campaign in my state (Pennsylvania) used these to great effect in a close election. I think they actually tipped the election. All the likely voters for Candidate A received these calls, generally at annoying times, and if you hung up it would keep ringing you over and over and over. The message started out "I'd like to tell you a few facts about Candidate A". People called the campaign headquarters of Candidate A to complain, and like you threatened to change their votes. Many were interviewed who said they had in fact changed their votes because of this incredibly annoying call.
The calls came from Candidate B. To comply with the law, you learned that fact if you stayed on the line all the way to the end.