Valdis Zatlers is not the first surprise candidate for a top political position in Latvia. Vaira Vike-Freiberga was only vaguely known for most Latvians, before she became the president in 1999. And I didn't know who Andris Skele was when he was chosen as the prime minister in 1995, after a deadlock in two-month long negotiations.
In both of those cases, the Latvian politicians chose a barely known person who did not belong to any political party. And in both cases, that person turned out to be more strong-willed than most of Latvian career politicians. Both Vike-Freiberga and Skele had a profound impact on Latvian politics, much more than it was expected when they were nominated.
I wonder if there is something deeper behind that. A weak person is less likely to become known outside of his/her own field. This may be why outsiders who ascend to top government positions in Latvia turn out to be stronger and more independent than the career politicians.
Curiously, people who know Zatlers describe him as a person of strong character. Will the parties who nominate him now be happy with him four years later? Or will they see him going in a direction that they didn't expect? As we see from the past, being dark horse does not imply being push-over.