1. TO DETER FUTURE LEAKS
US President Donald Trump has railed against leaks to the media but has had little success stopping them. Firing Mr Andrew McCabe could be a scare tactic to deter others from talking to reporters. The FBI's Office of Professional Responsibility recommended firing Mr McCabe as punishment for allegedly authorising the sharing of information with the Wall Street Journal in October 2016 and then misleading internal investigators about his actions.
2. TO WARN CRITICS
Mr Trump has promoted a flawed theory that Democratic groups allied with Mrs Hillary Clinton poured money into the state Senate campaign of Mr McCabe's wife while the FBI was investigating Mrs Clinton's use of a private e-mail server while she was secretary of state, thus buying improperly soft treatment from the bureau.
The problem with this theory is that Mr McCabe was not ''in charge'' of the Clinton e-mail probe at the time of his wife's campaign. However unfair Mr Trump's attack on Mr McCabe might be, firing him could be a warning to others that if the President thinks you are his enemy, he might come after you.
3. TO SHOW POWER OVER JEFF SESSIONS
Though White House spokesman Sarah Sanders had said Mr McCabe's fate would be up to Attorney-General Jeff Sessions, it was not hard to infer Mr Trump's desire. And Mr Trump has not held back when he disagrees with his attorney-general.
Mr Sessions' firing of Mr McCabe could be a sign that the President's bullying has worked to some degree, and made Mr Sessions more likely to do Mr Trump's bidding.
4. TO TARNISH THE SPECIAL COUNSEL'S RUSSIA PROBE
Mr McCabe was acting director of the FBI during the first few months of special counsel Robert Mueller's probe of Russian interference in the 2016 presidential election.
The Office of Professional Responsibility's recommendation to fire Mr McCabe is based on his alleged role in a leak related to the Clinton e-mail investigation, and not anything to do with the Russia probe.
But with a little muddying of the waters, Mr McCabe's firing could be used to further impugn the integrity of the special counsel's work.
5. TO LOOK LIKE A CHAMPION OF THE WORKING CLASS
Appearing on Fox & Friends last Thursday, counsellor to the President Kellyanne Conway said Mr Trump, in Missouri a day earlier, had met ''a tearful cafeteria worker... saying thank you for my tax cut''.
Host Ainsley Earhardt then drew a line to Mr McCabe, saying: ''He gets to live on a pension that that hard-working lady has to pay for, for the rest of his life? It's just - it doesn't seem fair.''
Ms Conway said: ''On the broader issue of fairness and accountability, it's part of how Donald Trump got elected in the first place.'' One ready-made argument is that canning Mr McCabe is a way of looking out for working-class voters.