"Was" and "were", which is correct in this context? Can a mood be established in a terminating clause?

I'm not sure I understand what establishes a mood. Does a sentence have to establish a mood at the begining or can a mood be established in a clause at the end?

And, that's if he could get elected after 35% of Americans turned out in opposition to both parties and a new popular movement was seeded.

Or,

And, that's if he could get elected after 35% of Americans turned out in opposition to both parties and a new popular movement were seeded.

In both of these we're talking about a scenario that doesn't exist. The top one clearly sounds more right to me.