You know you're in trouble when Boris says you're not a serious politician.
Foreign secretary Boris Johnson has burst onto the campaign trail this morning, branding Opposition leader Jeremy Corbyn a "mutton-headed old mugwump" who can't be trusted with weighty policy decisions.
Writing in the Sun, Johnson warned voters not to dismiss Corbyn as "harmless".
"Do you have those feelings?" he wrote. "Have you ever thought the leader of the Opposition is an essentially benign Islingtonian herbivore? Have you felt a pang of sympathy for his plight? If so, fight it."
The foreign secretary, who owns an end-of terrace house in Islington, questioned whether Corbyn could handle the triple-threat posed by Russia, North Korea and the Islamic State, asking: "Where is Corbyn on any of these issues?"
Johnson has so far stayed quiet this General Election, prompting many to ask whether the Conservatives planned to hide him away until the vote on 8 June.
And his attack on Corbyn has sparked at least as much debate about his obscure language as his stance on foreign policy. The Sun was forced to include a "Boris Johnson glossary" to help readers navigate his opinion piece.
The controversial politician, known for stealing the limelight, confused commentators with the term "mugwump", a word dating back to 1884 meaning someone who is aloof and independent of party politics.
In a comment read out on the BBC Today Programme, Labour MP John Healy said "it's typical Boris Johnson, a childish insult you'd expect from an old Etonian".
Johnson appeared on the radio show and apologised "to mugwumps everywhere" for using the term in reference to Corbyn.