(CBS NEWS) -- "60 Minutes" has obtained a letter that indicates the government whistleblower who set off the impeachment inquiry of President Trump is under federal protection, because he or she fears for their safety. These rapidly developing events began Tuesday when Speaker of the House Nancy Pelosi ordered the investigation based on a phone call between Mr. Trump and the president of Ukraine. President Volodymyr Zelensky asked Mr. Trump for missiles, Mr. Trump asks Zelensky for "a favor" to investigate Mr. Trump's Democratic rivals.
Democrats say this is the type of collusion that was the focus of the Mueller investigation. And it appears Washington will be immobilized by this, 13 months before election day. President Trump says he is the victim of a Democratic smear, crooked media and treasonous spies. Tonight we will hear from the man in charge of the investigation, the president's lead defender in Congress and Speaker Pelosi who, for months, resisted impeachment.
Nancy Pelosi: We could not ignore what the president did. He gave us no choice. So it wasn't any change of mind. I always said we will follow the facts where they take us. And when we see them, we will be ready. And we are ready.
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