LONDON

“Is this presidential election really the most important in our lifetime?” That was the question asked, in so many words, by a concerned Brit at a discussion here a few days ago. His words were directed at the political analyst Larry Sabato, whose countenance had been beamed onto a conference-room screen like some giant electronic guru. Sabato didn’t blink. “This presidential election,” he replied, “is definitely the most important since 2008.”