The link below is to a Google rendering of a contemporary book with county by county returns for both the February vote where the mere calling of a secession convention was strongly rejected and the questionable vote in June ratifying the legislature's choice to leave the Union. The first election's returns start on page 33, the second on 48. The chapter starting on page 46 gives the contemporary Union opinion on the secession vote. A typical doubtful swing would be a county like Polk where secession was rejection 1,112 to 117 in the first vote, but approved 738-317 in the 2nd vote.
East Tennessee was certainly a stronghold of pro-Union, Jacksonian sentiment during the war, as were the counties of North Carolina just across the line, that tried to secede from Tarheel like West Virginia did, to form their own little "republic" they agreeably called Mayland. Having been imprisoned in my damaged (still repairing) house for going on two years now, Mayland would be an appealing place to visit next month, if I could get away.