Sorry for the wonkiness of this post, but perhaps somebody can help!
To test this hypothesis, I looked at the 270 precinct-by-precinct results for Measure D and generated a list of those voting for vs against. This part was easily generated with judicious use of awk and sort, resulting in the list of numbers to the right. The observant person will notice some duplication because the county clerk lists in-person votes separately from mail-in ballots.
We see only 6.25% of voters in precinct 10284 (located in the hills along Soquel Demo Forest) voted for Measure D, while 100% of voters in Precinct 40230 (all twelve of them, out beyond the Santa Cruz County Fairgrounds east of Watsonville) voted for the transportation sales tax.
A peek at my town in the Santa Cruz Mountains along Highway 17 shows many of my neighbors voted against widening Measure D, as did the majority of those living in the far western reaches of Santa Cruz County. (Confounding my hypothesis — I think those living in this part of the county are most likely to vote against taxes just on general principle. We can perhaps look at who voted for Trump or Gary Johnson in the county to guess if this might apply.) Those who live near the UCSC campus, conversely, seem to have voted in favor of Measure D.
It’s difficult to find tends within the county with this manual picking and choosing, and I don’t have the skills to map these precinct numbers and voting results onto a map. Who knows how to translate this list into a handy visual? A map of the precincts can be found here. I’ve looked at the source for clues on finding shape files but have come up empty so far. TIA!
0.0625 10284 0.0909091 20241 0.0909091 50174 0.0909091 50503 0.153846 50096 0.263158 10236 0.285714 10551 0.333333 50148 0.352941 50163 0.357143 20421 0.357143 30046 0.359375 54071 0.363636 20093 0.363636 50222 0.375 10523 0.375 10533 0.380531 50342 0.411765 10146 0.418182 50415 0.444444 50144 0.458333 50082 0.465649 50265 0.468085 50083 0.468553 43741 0.478261 20244 0.478261 50243 0.486486 10700 0.494118 40270
XXX MAJORITY 0.5 10151 0.5 10152 0.5 10163 0.5 10232 0.5 10237 0.5 10287 0.5 10653 0.5 12010 0.5 20222 0.5 43711 0.5 50015 0.5 50090 0.5 50146 0.5 50284 0.5 50453 0.5 50503 0.506667 30020 0.508929 10161 0.514085 50232 0.514493 43710 0.515789 50211 0.521978 43741 0.526316 50263 0.540984 10291 0.543478 54061 0.547619 10234 0.550847 50382 0.551724 43260 0.552239 30010 0.555556 20013 0.555556 31690 0.557423 14121 0.55814 50480 0.56351 50191 0.566038 50061 0.569106 43621 0.569182 14121 0.571429 10581 0.572165 43631 0.573099 20020 0.573427 50204 0.574074 14141 0.575163 50161 0.575758 50061 0.577206 50121 0.578512 50021 0.57931 10201 0.579618 30041 0.580247 43610 0.580488 50221 0.580645 50232 0.581006 40162 0.581197 40162 0.583333 50341 0.583333 50492 0.583691 40071 0.585938 50521 0.587031 20041 0.587838 43441 0.587963 50157 0.588785 20341 0.59009 50102 0.590308 50091 0.590643 43710 0.591837 50141 0.594595 10292 0.59633 50401 0.6 30020 0.604082 50204 0.606897 10603 0.607287 50183 0.607595 50021 0.608696 50191 0.612245 43731 0.612903 10231 0.613636 40270 0.61413 10351 0.616725 50211 0.617188 30080 0.617747 54070 0.61859 50092 0.619048 20392 0.619266 50401 0.619718 20044 0.620098 50121 0.620968 50111 0.621622 30030 0.621723 20041 0.623529 43410 0.624183 54010 0.625 10382 0.62623 50023 0.627273 51770 0.628205 43631 0.629787 50091 0.629969 50102 0.630508 43731 0.630631 23312 0.631799 43410 0.632075 10260 0.633229 54031 0.633588 31250 0.634146 54010 0.634304 40161 0.634921 10220 0.635338 54031 0.635688 50157 0.635945 54061 0.636364 10690 0.636628 20011 0.637195 50111 0.637363 50092 0.638436 10060 0.638614 54051 0.64 20341 0.640351 50112 0.640449 50382 0.641509 50233 0.642202 54020 0.642276 50541 0.642424 43110 0.642534 50183 0.643357 10080 0.643705 30041 0.643836 20221 0.643836 50023 0.644068 10381 0.644769 20354 0.64486 30030 0.644928 31342 0.646154 50112 0.646465 50341 0.647059 20551 0.647303 20011 0.647577 20061 0.648045 40071 0.648415 50161 0.648649 20020 0.649254 12023 0.65 20381 0.650407 20013 0.651709 20320 0.651741 54051 0.651822 50203 0.651948 20300 0.652174 10142 0.652174 50181 0.652284 10381 0.652361 20101 0.652778 10161 0.652866 20221 0.653061 43610 0.653137 20044 0.654412 50381 0.654618 31710 0.656085 54020 0.656836 50141 0.657143 12010 0.6575 23311 0.658182 20402 0.658537 50203 0.658621 22010 0.660256 20101 0.660377 43732 0.66092 20330 0.661538 20150 0.6618 20320 0.662207 31020 0.663043 50202 0.66318 20280 0.663609 20551 0.663793 20232 0.664062 22040 0.664948 11010 0.665399 31490
XXX SUPERMAJORITY 0.666667 10240 0.666667 10572 0.666667 30121 0.666667 50221 0.667774 10603 0.668539 31400 0.668639 10020 0.668693 20351 0.668712 10270 0.668831 10490 0.669231 23360 0.669725 43621 0.669903 50522 0.67027 20260 0.670807 31011 0.671171 43501 0.671518 10294 0.672619 54070 0.672727 10286 0.673469 10521 0.674556 31300 0.674797 31342 0.675 10295 0.675258 10170 0.676364 10060 0.676471 20520 0.677419 10162 0.677419 50250 0.678851 10190 0.679012 10283 0.680328 43501 0.680723 50040 0.680912 20541 0.681159 10164 0.681234 20280 0.681633 10351 0.68169 10130 0.681818 43711 0.681922 20351 0.682266 31710 0.682464 20330 0.683284 51090 0.683962 10294 0.684729 20061 0.684746 20520 0.686207 11120 0.686486 31450 0.687023 43110 0.6875 10260 0.687671 10130 0.688797 43441 0.689189 22010 0.690037 10090 0.690141 10201 0.691176 10144 0.692478 22050 0.693069 12023 0.693642 10281 0.693649 22050 0.694737 31210 0.695946 10080 0.696078 10020 0.696133 43540 0.696246 31140 0.697143 10620 0.697531 10240 0.697674 20541 0.69863 31480 0.7 10763 0.7 30100 0.7 50146 0.70098 20242 0.701005 12024 0.701493 22040 0.701613 20300 0.701807 20232 0.702479 31490 0.703704 31240 0.704319 10100 0.704348 10490 0.704453 31580 0.705263 31240 0.705556 23311 0.706667 31580 0.707317 10141 0.707736 20260 0.708075 31160 0.708738 31011 0.709581 31150 0.709906 11010 0.710345 23312 0.710383 31300 0.711712 43220 0.712025 10190 0.712551 51090 0.714286 31450 0.714286 50480 0.714697 10100 0.715232 20243 0.715328 31050 0.716418 20354 0.717241 31070 0.719178 10090 0.719512 10144 0.72 10410 0.720365 31050 0.721823 40161 0.723881 31560 0.72549 50040 0.725979 10170 0.727273 31250 0.728947 51080 0.731118 10310 0.731569 31140 0.731707 20150 0.732861 31150 0.733485 12024 0.734513 51080 0.73545 11120 0.736842 31560 0.73743 10270 0.738609 31030 0.738739 31210 0.738854 10620 0.73913 20243 0.73913 43200 0.73913 51010 0.739362 10410 0.741313 43540 0.741379 51010 0.742647 10220 0.742972 10110 0.744063 31070 0.744361 31530 0.745098 10281 0.745583 31030 0.746479 23360 0.748175 20402 0.75 10352 0.752907 10110 0.75463 31610 0.757576 31301 0.757679 31480 0.758621 50521 0.760563 31013 0.761468 31301 0.763736 43200 0.767516 10310 0.775 10682 0.775 20242 0.776675 31400 0.777159 31020 0.777778 31013 0.780702 51770 0.781818 31160 0.782383 31190 0.78655 31530 0.787611 31190 0.793233 31650 0.795181 43100 0.797101 43100 0.798611 43220 0.8 31600 0.807018 51620 0.82 31600 0.821429 20231 0.831395 31690 0.833333 31650 0.857143 10145 0.866667 31610 0.866667 31630 0.875 31630 0.958333 40010 1 40230
Take a look at https://star-transit.org/2016/11/09/measure-b-fails/. If this is what you want, I can at least explain how it works, and might have time to create if for you.