Plaid Cymru president Ieuan Wyn Jones has said he would consider backing a referendum on extra powers for the National Assembly.
Speaking on Question Time on BBC1, he was asked whether a proposal for increased power for the assembly should be put to a vote.
Mr Jones said he had an open mind on the issue.
He wasn't convinced of the need, but certainly would not rule it out, although it was not in the Plaid manifesto.
He said the step was not a significant one, and he was prepared to listen to people's views.
Mr Jones said it was possible that a future tax-varying assembly could reduce taxes in some circumstances.
For instance, the manifesto proposes that corporation tax should be cut in the Objective One areas of West Wales and the Valleys.
He predicted that a big vote for Plaid Cymru would be a mandate to give the assembly the same powers as the Scottish Parliament.
Mandate for change
If there was substantial support for Plaid Cymru at the general election, and after that the party became the government of Wales, that would be a mandate for a parliamentary bill to turn the Assembly into a tax-varying and law-making body.
Mr Jones said he was not worried that Plaid's proposal to raise income tax to 50p in the pound on earnings over £50,000 a year would lead to a brain drain from Wales.
He said it was a "very modest" proposal, and tax take in Wales from the highest incomes was the lowest in Europe.
Asked whether he would turn to the monarchy or Europe if Britain "collapsed", he said royalty had to modernise if it was to survive.
He said he had no strong views either way on whether the monarchy continued or ended.
Mr Jones said he was very surprised that the words racist and xenophobic had been applied to comments by Plaid Gwynedd councillor Simon Glyn about English people coming into Wales.
Mr Glyn had said that English incomers should be monitored and were a drain on local resources.
Mr Jones said he believed passionately in a multi-ethnic and multi-lingual Wales, and that what Mr Glyn had said was not right.
"When I say Plaid Cymru is a party for the whole of Wales I mean that," he said.