The following sample code shows how you can delete a poll including its answers.
[C#]
| using CMS.Polls; 
 ... 
 string pollName = "testingpoll"; 
 // Get poll info for the specified code name PollInfo pollObj = PollInfoProvider.GetPollInfo(pollName); 
 if (pollObj != null) { // Delete the poll PollInfoProvider.DeletePollInfo(pollObj.PollID); } | 
Page url: http://devnet.kentico.com/docs/5_0/devguide/index.html?deleting_a_poll.htm