For the Welsh Liberal Democrats, there's a lot riding on today's regional pay vote in Brighton. (There are more details here.) If they succeed they'll have set their party against any attempt by the Coalition Government to introduce different public sector pay levels in different parts of the UK.
It's a major challenge too for Eluned Parrott who only became an AM last year but is leading the debate which starts at 4pm this afternoon. She told me that she wants to win over heads as well as hearts, presenting economic arguments against regional pay as well as appealing to a sense of fairness.
She and leader Kirsty Williams have also seized every opportunity to try win over senior figures in a series of formal and informal meetings. Danny Alexander, who earlier this year said he was 'keen' to see local pay, will be in the front row. Have the Welsh Lib Dems succeeded in changing his mind?