A vote transfer poll asks the electorate about how they voted in the last election and how they would vote if the next election was now. With the result from both questions one could build a matrix of vote transfer, say: 77% of Party A voters admit maintaining their vote, whereas 12% admit voting for Party B. How confident can we be in these estimates? How do they relate to sample size? How big does the sample need to be for required degree of confidence? Does it depend on the number of parties?
EDIT 1: To give you an example, here is what such a matrix would look like (columns for previous vote, rows for future vote intentions):
All the columns sum up to 100%, since every voter of every party must choose the same or another party, choose not to answer (Nr) or say they don't know (Ns).
How confident can we be in the values of each cell? Does it depend on the sample represented on each column?