關於現在完成式的問題?

你的句子　有２個錯誤：

１．沒有注意到動詞的意義：
The election has started since 8 AM. (very questionable）
因為start, die, find, kill 是一個瞬間的動作　開始以後　在結束之前　就不會再有一個開始
我們不說：
He has died since 2008.
而我們說：
He has died for 8 years.
He has been dead since 2008.

２．對主詞election 的誤解：

election與 poll有一個很微妙的差別：
前者可以包含所有的選舉活動　後者指包含＂投票＂的這個動作

The poll has been open since 8 AM. (this is even better)
．
所以嚴格來說　

選舉在上午八時開始，現在是同日傍晚六時，選舉還未結束.

是錯誤的．因為只是＂投票＂是在今天早上８點開始　而選舉活動　早就在幾個月前就開始了．

３．結論：

The election has started. (good)
The poll has started. (good)
The poll has started for 8 hours. (OK)
The poll has started since 8 AM. (avoid - see reason 1)
He has died since 1912. (avoid)
He has been dead since 1912. (good)
He has died for 105 years. (OK)
The election started at 8 AM. (good)
The poll has been open since 8 AM. (this is even better)

The election has not finished yet.
最好說法能滿足你的所有需求The election has been continuing on since 8 am.