Trump goes after FBI's Andrew McCabe on Twitter, again

President Trump took aim at Andrew McCabe, Deputy Director of the FBI, again Sunday in a morning tweet, quoting Fox News. Yesterday, he tweeted about McCabe's reported plans to retire.

The backdrop: The Trump administration, as well as several top Republicans, have questioned whether the FBI under James Comey conducted an unbiased investigation into Hillary Clinton's use of a private email server. McCabe was Comey's Deputy Director and had an oversight role during the probe. He also told a House Intelligence panel last week that Comey had told him about Trump's alleged request for "loyalty."

Why it matters: Trump is attacking senior FBI officials at a time when the bureau is working hand-in-hand with Robert Mueller, a former FBI director, on the Russia probe.