Stilly River Sage:

Hush! Don't disparage polls anywhere that Mr. Rove might hear you.

Polls are, indeed, useful for limited purposes. I am, however, more inclined to place whatever credence they deserve in an independent organization's product (like Gallup) than in a poll done by or at the behest of a political party or interest group. Gallup has been asking essentially the same questions about every sitting president at least as far back as those reported above. And, looking at the Gallup methodology, these are not an average of one or two data points over the term of office. The questions are presented fairly regularly and responses are set up as "flow charts." I am not certain that the ancient archives are available on line, but more current data can be accessed without too much difficulty.