cos

Yes. That's a separate question in most polls, and it is useful. That by itself doesn't help you predict a future election outcome, but it's useful for developing or judging strategies, and provides useful context for other information. There are various other things in polls that can be useful, though not necessarily for predicting the outcome. However, the "who would you vote for today?" portion of the polls, the part that's reported prominently, is NOT USEFUL. Not really even for name recognition - for that, you want to look at the appropriate portion of the poll.