In The Walking Dead midseason finale, "Hearts Still Beating," it looked like Spencer had taken Father Gabriel's advice from the previous episode to heart, though not quite in the way anyone expected. Spencer decided to come up with a plan. He wanted to be like his mother, a leader and former Congresswoman, and he set out to prove it by ingratiating himself with the Saviors any way he could. However, he also decided to undermine Rick in the process. Like every character who has tried to do that before him, it cost Spencer his life. So is Spencer really dead on The Walking Dead?
That would be a pretty definitive yes considering he was left bleeding out on the sidewalk in Alexandria. Before things went bad, Spencer thought he was doing well. He settled down for a drink with Negan while playing nice with every Savior who crossed his path. He offered them supplies, endured some mild flirtations, and practiced his pleasantries in the mirror so he would be ready. He decided to be proactive by vocally supporting Negan – while making sure to let Negan know that Rick wouldn't be a team player. Spencer wanted to be the leader instead of Rick, and his underhanded way of going about it (by waiting until Rick was out) didn't sit well with Negan at all.
Though Spencer wore his nicest power outfit to his interview with Negan, his characteristically weaselly behavior got in the way of him making any real strides. Spencer thought he should be the one to replace Rick because thanks to his mom Deanna, leadership was in his blood; Spencer apparently hadn't noticed that no one liked him. Negan didn't appreciate Spencer going behind Rick's back because, in his opinion, it proved that Spencer was a coward who wanted other people to handle his business for him. He wanted Negan to do his killing for him so that he could reap the benefits without getting his hands dirty. Spencer had no guts.
Negan then went about proving that statement by disemboweling Spencer in the middle of the street and leaving him there to die. It was a scene taken almost directly from the comics that inspired the show, down to the dialogue. The Walking Dead appears to be following the comics very closely throughout the entirety of Negan's storyline, bringing his more memorable moments and lines to life.
R.I.P., Spencer. Something tells me no one will be that sorry to see you go.