"Sour Grapes" have been a major determinant in Jury decisions...always has been; always will.
Personally if I were on the Jury my vote would be based on who was the most proactive and best Survivor player that season in the true spirit of the word "Survivor"...Period. But historically we know votes don't go that way.
Getting back at someone who did you wrong isn't so much about playing the game of Survivor as much as it's a basic fiber in human nature. For some individuals that fiber runs deeper than for others, but a player would be remiss to not consider this emotion when making a decision in the game.
In Marquesas Pappy and Neleh made a post-merge flip changing the course of the game. When Neleh sat at FTC jury members said straight-out they would not vote for her due to her (and Pappy's) flip. This handed the win to Vecepia, the quinessential UTR player.
Progressing to a middle season do I even bother asking the rhetorical question if Amb"a"s victory was a result of the vengeful reaction to Rob M's lying, deceitful behavior, and backstabbing?
Looking at a recent season, no one can convince otherwise the Cirie' vote for Perv-ati in Skankivor: Micronesia was sour grapes against your favorite Survivor gal when Amanda's sole vote took Cirie out of the game.
As for your hypothetical situation...if a female F3 formed and systematically picked off JTand Stephen next...Yes, I personally feel Stephen would vote against Taj. JT, I'm not so sure about. But one thing is for sure; Steve would have a few days on the Ponderosa to be whispering in JT's ear and influencing him one way or the other. And we don't have to go any further back than last season to know voting blocs have been established in Sequesterville.
Of course this is all hypothetical and we'll never know. Taj's only chance at winning (and a slim chance at that) is to continue playing the "I am not directly responsible for any of you sitting on the Jury" card and remain likable.