Calculating level of confidence from margin of error

Someone please help me. I have this question on one of my math assignments and I can't figure out how to set it up. I've asked on other forums but they've all been extremely rude and unhelpful. This is the question

"select a political poll and note the margin of error, sample size, and percentage favoring the candidate for each. Determine the level of confidence that must have been used to obtain the margin of error given, knowing the percentage favoring the candidate and number of participants. Does a pattern emerge?"

So, I selected a poll and the margin of error is +-2.73, the sample size is 1282, and Candidate A: 40, and Candidate B: 44. How do I solve this/set it up? Also, how do I find the standard deviation?