I have not set foot on Taiwan for mroe than two decades. But my impression about "装有高音喇叭的敞篷车，播放他们支持的候选者的竞选宣言" is these were campaign workers (not supporters) in campaign-owned 4 x 4 trucks (instead of convertibles 敞篷车).
(c) "于右任的诗歌，'葬我于高山之上兮，望我故乡；故乡不见兮，永不能忘。' "
(i) 古遠清, 台灣文壇的「實況轉播」: 一位大陸學者眼中的台灣文壇. 秀威出版, 2013, pages 100-101 https://books.google.com/books?i ... 3%80%82&f=false
("于右任寫於一九六二年的《天的悲歌》")
(ii) from a website within China: "于右任的《望大陆》(又名《国殇》"
(iii) I have not heard of this poem (and I doubt most Taiwanese around my time in Taiwan did).
I had the same conclusion back in Taiwan: it is a waste time to go to campaign gatherings to listen to talks. First and foremost, it is like in US* where many gave speeches before the headliner arrived, talked briefly and left quickly.
* This is the format most of the time, but once I went to a campaign stop of Massachusetts Republican governor Bill Weld seeking re-election. Only two score (me included) showed up to hear him out (because everyone knew he would win by a landslide) and he was the only talker (who delivered a short speech).
(ii) "接下来我又参加了民进党和2014年太阳花学运后新成立的政党时代力量的街头集会。民进党的集会活动的主持人在舞台上说马英九政府的八年卖了台湾，完全没有做好事，似乎年轻人工资过低的所有责任也都在马政府。而聚集了很多年轻人的时代力量党的集会上，一位歌手用闽南语一遍遍唱 * * * 他们讲话都显得很夸张和煽情。"
(A) 时代力量 is a one-year-old party. But 民进党's campaign gatherings always use 闽南语 only. I wonder how the author could comprehend. (maybe his Taiwanese friend(s) translated.)
(B) "夸张和煽情." Exactly. The contents of many campaign speeches were innuendos.