If random sampling were used for this survey, what is the margin of error for this estimate at the 95% confidence level?

A Gallup poll of 2,000 Russians taken between April and June 2014 (after the Olympic games in Russia and the annexation of the Crimean peninsula) showed that 83% approved of President Putin's performance. If random sampling were used for this survey, what is the margin of error for this estimate at the 95% confidence level? (In fact, Gallup uses weighted sampling and, based on it, reports a margin of error of 2.7%)