By Vaughan Roderick BBC Welsh affairs editor

Mr Jones has regained overall leadership of the party

Since their stunning success in the first Welsh assembly elections in 1999, the party has been losing ground on several levels.

Assembly seats have been lost, Westminster and European seats have been lost, control of councils has been lost - so why does the party exude such optimism?

They could be fooling themselves, of course, or attempting to fool political journalists or opponents.

Private polling

But political observers ignore such signs at their peril.

Sometimes the party workers are right and the received wisdom is wrong - as the Liberal Democrats proved in Ceredigion in the general election.

Plaid recently published the results of private polling suggesting they are now in a position comparable to their standing in 1999.

Dafydd Wigley has returned to front-line politics

While the other parties have, predictably, dismissed the results, the poll was professionally conducted and has buoyed the party's spirits.

So Plaid starts its conference in Swansea in surprisingly good heart.

The long saga of its split leadership appears to have been resolved with assembly leader Ieuan Wyn Jones re-emerging as the overall leader of the party.

Like a weeble, Mr Jones wobbles but he won't fall down.

Publicity coup

The party also now boasts that it has the largest staff of any political party in Wales and has developed a series of eye-catching policies to be release over the coming months.

The recent plan to offer �5,000 grants to first-time home buyers is a classic example.

Experts might well question its practicality and effectiveness but it was publicity coup certain to play well with sections of the electorate.

Expect more of the same between now and May.

As in most pre-election conferences there are few debates likely to spark major controversy.