Margin of error is 3.9%. The article should have said, evenly split at best. This is not a good sign for such a weak story in a very pro-gay newspaper.
This kind of proposal brings out people who, even if they are usually quite liberal, just can’t accept the idea of homosexuals marrying. They won’t say it publicly - but they talk about it around the kitchen table with family and friends, and object to the idea vehemently.
I expect that new constitutional amendment to pass with percentage to spare.