Since 1984, when the question has been asked on exit polls, “taxes” has never been the top issue for voters. Voters who do say it’s the top issue for them cast their votes in substantial numbers for Republicans.
In polls, Republicans generally make taxes a higher priority than Democrats do. Somewhat worrying for the GOP then is that in recent polls they appear to be losing their advantage as the party better able to handle the issue. In June, the Republicans had a 4-point advantage on the issue in the NBC News/Wall Street poll. In their December poll, the Democrats had a 4-point advantage. These responses could be read as a commentary on the tax bill, but it is more likely that they reflect more generally negative views of the GOP.