The passage deals with the controversy in the Conservative Party over the formula for Britain's exit (Brexit) from the European Union proposed by the prime minister, Theresa May, during a meeting of her cabinet at her country residence, Chequers.
This formula is strongly opposed by many members of the party, including her former foreign secretary, Boris Johnson, who afterwards resigned from the government to oppose it.
In an extravagant metaphor in his newspaper column Mr Johnson compared the likely impact of the Chequers plan to that of a suicide vest. That's to say: it would destroy the British constitution.
Steve Baker, a former minister in the Brexit department, also resigned from Mrs May's government in July in protest against the plan that she proposed. (He and many other Tories consider that it will not amount to the complete exit from the EU that they demand.)
Another former government minister, Nicky Morgan, who is supportive of Mrs May, condemned the comments made by Boris Johnson in his newspaper column. She says that Boris, who came to politics via journalism, has to decide whether he wants to be a journalist or a politician. (That's to say: he should not try to be both at the same time. Boris remains a Conservative MP while he uses newspapers to voice his opposition to government policy.)
Nicky Morgan thinks that he has already made this decision. The expression sort of softens her statement. (Sort of and kind of are expressions that people use in conversation all the time, both to catch their thoughts and to modify their comments.)