Credit goes to Pope Francis and the local Catholic Church. Via the Associated Press:
Preliminary referendum results have shown that Slovenians have rejected a same-sex marriage law by a large margin. The results released Sunday by authorities show 63 voted against a bill that defines marriage as a union of two adults, while 37 were in favor. The results are still incomplete, but are unlikely to change significantly in the final tally. Parliament introduced marriage equality in March, but conservative groups, backed by the Catholic Church, have pushed through a popular vote on the issue.
The final tally is being posted here.