Big "WHAT?!": The scene where Steven explains to Sadie what happened to Lars starts with her yelling "What?!" over an Establishing Shot of the Big Donut.
Bittersweet Ending: Dewey lost the election, but he's not bitter about it, citing that Nanefua will make a better mayor than him. Steven finally understands the emotional turmoil he put Connie through and wants to talk to her, but it looks like she's still understandably upset with him.
Connie's anger at Steven for his Heroic Sacrifice is understandable, given it implied he didn't trust her and that they could've thought of something together. Steven was in a stressful position where his loved ones (including Connie, his Living Emotional Crutch) were about to be taken away, with no way to get them back; of course he would try and save them the best way he saw.
The townspeople are completely right that Dewey's Head-in-the-Sand Management style makes him a terrible mayor and that he's more concerned about himself and his success than he is of the town. However, they are using him as a scapegoat, blaming him for things that aren't his fault and that he had no control over. It's Nanefua's acknowledgement that they should stop pointing fingers and instead "share responsibility for the welfare and safety of Beach City, together!" that ultimately convinces Dewey that she would make a better mayor.
The situation between Steven and Dewey perfectly mirrors that between Steven and Connie — which is not lost on Steven. Dewey is right that Nanefua will make a better mayor and that withdrawing from the race was probably the best thing he could have done in service of the town, but Steven is also right to be upset that Dewey would just give up like that, after all Steven did to help him.
Condescending Compassion: Steven believes that Connie should've been happy that he gave himself up, and cites how "brave" it was of him to do that. He has a Jerkass Realization about it after Dewey's failed campaign.
The debate uses a banner for "Beach-A-Palooza", shown in "Steven and the Stevens" and "Sadie's Song", that's been hastily modified to read "Speech-A-Palooza".
The cue cards Steven made for Dewey speech are said to includes jokes about Ocean Town, something Dewey did in a speech in "Political Power".
Didn't Think This Through: Connie calls Steven out for giving up so easily instead of trying to come up with a better plan, and it's made clear that he didn't think of how his loved ones would be hurt by his Heroic Sacrifice.
Disapproving Look: Lion gives one to Steven for his insensitivity to the emotional pain he put his loved ones through before departing with Connie.
Facepalm: Steven does this when Dewey promises to replace Lars instead of finding him, while his parents and Sadie are in the crowd.
Fantastically Indifferent: Following the previous episodes, while the public reacts to the abductions, given it led to multiple kidnappings (and with one of the victims not being fully rescued), it's still treated as a mundane crime would be.
Gilligan Cut: When Steven promises to help Dewey practice all night for the debate, it immediately cuts to daytime, showing Steven and Dewey with bloodshot and baggy eyes from lack of sleep.
He Had a Name: When Dewey finds out one of the abducted humans hasn't made it back yet, Sadie angrily tells him Lars's name, and Dewey only knows him as "Donut Boy".
Heroic Sacrifice: Deconstructed. While Steven turning himself in may have been done to save everyone else, everyone was still worried sick for him, and Connie implies during her What the Hell, Hero? moment that him sacrificing himself was, even if he didn't mean it like that, an indication that he didn't believe that they could help him. His Heroic Sacrifice also led to Lars getting trapped and dying on Homeworld, with him coming back to life only thanks to his magic tears. Steven, however, believes that Connie should've been happy at his act and cites how "brave" it was of him to do that. He does eventually have a Jerkass Realization, but by the time that happens, Connie is refusing to talk to him.
I Did What I Had to Do: Steven believes that giving himself up to Homeworld was necessary, though Connie thinks it wasn’t.
Immediate Sequel: The episode begins seemingly minutes after the end of "Lars' Head".
Innocently Insensitive: Steven acts as if turning himself in to Homeworld was a good choice, and honestly doesn't seem to notice the anguish it put everyone else through. Him acting like this only makes Connie more frustrated with him.
Connie: But I'm hurt! Steven: No you're not! You're safe! You're here, I'm here, we're safe, everything's fine! Connie: It's not, though. Steven: You know, it was a tough decision for me to make. But it had to be done. Connie: You don't get it. Steven: ...Get what?
Ironic Echo: When telling Steven she's disappointed that he gave up so quickly, Connie says "I believed in us! We could have done it together!". At the end of the episode, Steven says the same thing to Bill after he drops out of the election. The irony is not lost on Steven.
After Dewey's monologue about how the Mayor is blamed for everything, Nanefua realizes and admits that she's usually the ringleader when people point fingers at Dewey, and so resolves to be better and help the community come together and solve their problems instead of just blaming others.
Steven realizes the situation he put Connie through while trying to convince Mayor Dewey to continue his campaign.
Know When to Fold 'Em: Dewey concedes the race during the debate when it becomes clear that Nanefua is the better choice.
Mama Bear: Lars' mom throws a tomato in Dewey's face when he promises to get a new Donut Boy for the Big Donut instead of trying to get him back home.
Mis-blamed: Subverted in-universe. Even after Steven admits to the town people he was the one responsible for the kidnappings, they all consider Dewey to be the one fault for not doing anything about it just because he's the mayor.
Moral Luck: Steven argues him getting back to Earth and Lars being (moreor less) safe validates his Heroic Sacrifice, even though that depended largely on unforeseeable occurrences. Connie is unconvinced.
Steven asks the townsfolk not to blame Mayor Dewey for the abductions, pointing out he just keeps a low profile and doesn't get involved in these sorts of things. Some angry townsfolk point out that, as the mayor, he's the town's leader and should be getting involved in these things.
Ability to handle a stressful position of leadership is Dewey's primary argument for reelection, but he says this with bloodshot eyes, Exhausted Eye Bags, and sweating profusely (both because of the stress of facing electoral competition and staying up all night to practice his speech).
Dewey: Most people can't handle that kind of pressure. (Dewey's eyes go out of focus) But I can!
Not Hyperbole: Steven promises to help Dewey practice for the debate all night. Cut to the next day, where both have bloodshot and baggy eyes, indicating they took that promise literally.
Permanent Elected Official: Dewey's run unopposed in every election until this episode. He finally loses the position to Nanafua here.
Poor Communication Kills: Subverted. Connie makes it painfully obvious she's upset at Steven for giving up in the fight with Aquamarine so quickly, but Steven doesn't really get why she's upset until the end of the episode.
Produce Pelting: Lars's mother throws a tomato in Dewey's face after his response to Lars being lost in space is to promise to hire someone else for the Big Donut. She's ready with another during the debate, but never gets to throw it.
Pun: Nanefua has a megaphone with "Nana-Phone" written on it.
Rabble Rouser: This episode provides a Deconstruction of the concept. While Dewey's Head-in-the-Sand Management is a genuine issue, he goes with it mostly to avoid inciting panic. Nanefua is often the one to escalate problems and is typically the first one to point fingers at Dewey, leading to exactly the kind of problems he's trying to prevent. The trouble with her approach is that it often turns Dewey into The Scapegoat over things that he can't control and just makes things worse instead of prompting a solution.
Given that this is the immediate aftermath of Steven coming back after turning himself in, it's no surprise that his guardians are extra protective of him.
Steven thinks his Heroic Sacrifice should be seen as brave, but Connie tries to explain to him that him giving up and sacrificing himself was basically saying that he didn't believe they could beat Aquamarine and Topaz. She also points out that the sacrifice caused Steven's loved ones, especially his father and the Gems, to go through tons of emotional pain because they all thought he was dead. When Steven doesn't realize this, she and Lion leave in frustration.
After Sadie learns about Lars' Disney Death and the fact that he's still on Homeworld (albeit with some nice gems who are also hiding from the Diamonds), she pretty much freaks out and breaks down in tears. Lars might have been brought Back from the Dead, but her co-worker, friend, and possible crush still died. Lars' parents also aren't happy with what happened to their son.
Dewey's Head-in-the-Sand Management finally catches up with him after the alien abductions, as it caused most of the town to scapegoat him since he was their leader and he didn't really do anything about it.
Steven may be a loving, magnetic person, but he has zero experience when it comes to mayoral elections.
Dewey, having run unopposed his entire life, has no idea what to do when someone is actually running against him.
Connie is not instantly ready to forgive Steven the moment he finally recognizes what's wrong.
The Scapegoat: People assume Dewey could have done something about the Alien Abductions, even though the acts were committed by nigh-unstoppable, superpowered aliens and ended before it became public knowledge. That said, Dewey does have a history of Head-in-the-Sand Management, and even he seems to recognize it. Notably, Nanefua focusing more on what's best for the town and not just blaming him is what convinces him to step down.