You're incorrect. Spencer flipped because McCrae flipped. You have it backwards.
Respectfully, Spencer didn't see anything. If Helen wouldn't have run to him and spill EVERYTHING to him, he would still be stumbling in the dark hoping when he hit the wall that it may contain some broil for him to try and figure out what just happened.
After Helen told him and that when Spence saw the writing on the wall and was trying to save his a.ss. He gave Howard the heads up and Howard looks like he still MC whereas Spence is like lets go back to the "minority alliance"
Also Spencer tried to warn Jeremy, .but Jeremy refused to believe it. Said (Jessica) was just following their instructions on what to say to Elissa's group.
In addition Spencer was trying to convince McCrae that he didn't need to vote to evict Elissa. It was McCrae's idea to throw the hinky vote. Spencer really wants to dump the MC right now and wants McCrae to come with him and Howard and show solidarity against the other side (Jeremy, Aaryn etc....)
McCrae was telling MC he was going to vote out Elissa and told the other group he was going to vote out nick but he also told the MC that he was lying to the Elissa group, he was truly going to vote out Elissa until Spence came to him and said lets vote Nick
yes, McCrae said to someone "make sure Jessica is voting out nick" but he was playing them all this time and was planing to vote out Elissa and blame the vote on someone else in the "Elissa group"
Spencer always wanted to flip because the logic of keeping Elissa, no matter what people say, was always unassailable. It is why Judd days ago (b4 evicting nick), pointed out everyone pushing to dump Elissa must be working with the other side. Then helen told him everything and seal the deal
and if you watching the feeds the same day nick got evicted, McCrae who wanted to throw a vote to evict Elissa but Howard talked him out of it. McCrae wanting to vote Elissa out. If Spencer was smart, he would have agreed with him .