Why was the presidential election of 2000 controversial

The returns showed that Bush had won Florida by such a close margin that state law required a recount. A month-long series of legal battles led to the highly controversial 5–4 Supreme Court decision Bush v. Gore, which ended the recount. The recount having been ended, Bush won Florida by 537 votes, a margin of 0.009%.

Explanation:

The election came down to a recount that was stopped by the Supreme Court.

slavery, abortion, donald trump, gay marriage, racial rights, immigration  

explanation:

anything that has been broth up to the supreme court is something of grate political divide   so just look as court cases

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