Governments call elections early, precisely because they can not be confident in maintaining their current, high level of popularity and performance to the next regular election. (blog.politics.ox.ac.uk)
Voters also understand that incumbents, who can be confident of performing strongly to the next regular election, have no reason to call an election early. (blog.politics.ox.ac.uk)
He initially refused to call any such elections, even though state law requires him to do so to fill legislative vacancies that occur before May in regular election years. (dailyreporter.com)