PRAGUE — With his rants against the European Union and gay rights, Vaclav Klaus has been no stranger to controversy in his 10 years as Czech president. But one of his final acts in power — a prisoner amnesty — has backfired so badly that he’s being accused of treason.

His portrait has been torn down in anger in schools and offices across the country in a rapidly evolving scandal that has cast a shadow over this weekend’s presidential election and tainted the post which, while largely ceremonial from the grandeur of Prague Castle, carries moral weight. It could also swing the outcome of the runoff vote that began Friday.