The following sample code shows how you can delete a poll including its answers.
[C#]
using CMS.Polls; 
 ... 
 string pollName = "testingSitePoll"; 
 // Get poll info for the specified code name PollInfo pollObj = PollInfoProvider.GetPollInfo(pollName); 
 // Delete the poll PollInfoProvider.DeletePollInfo(pollObj);  | 
Page url: http://devnet.kentico.com/docs/5_5r2/devguide/index.html?api_deleting_a_poll.htm