IT WAS likely that same-sex marriage will take place in Australia by the end of the year, Australian Marriage Equality campaigner Rodney Croome said yesterday.

And Tasmania will be first to decide on legislation this week. After passage through the House of Assembly, observers' counts indicate the 15 mainly independent upper house Legislative Council members are almost evenly split.

Hobart MP Jim Wilkinson was among a handful still anguishing ahead of final pitches from both sides before the debate begins on Wednesday.

''I know a number of people are still struggling with it,'' Mr Wilkinson said. ''I'm one of those.''

The state's Save Marriage Coalition led with an argument, likely to resonate in the deliberative chamber, that the bill is unconstitutional in Australia. ''This is the first question any legislator thinks of,'' said the coalition's spokesman and former Liberal senator, Guy Barnett.

The reformers' case in Tasmania emphasised potential economic benefits of marriage tourism to the state, with an assessment based on the US experience, claiming a first-mover state would bring tens of millions of dollars to the local economy.

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