Ynys Mon AM Ieuan Wyn Jones confirmed in July that he would attempt a political comeback.
Ieuan Wyn Jones resigned as party president in May
He decided to stand as Plaid Cymru group leader in the Welsh assembly - although that was only part of the post from which he resigned after the Welsh assembly election in May.
His previous role as president was split when none of the party's 12 AMs decided to go for the job.
At the time he said he had come under intense pressure from grassroots members from all over Wales and from senior party figures to join the leadership race.
"They believe that I have the qualities necessary to lead the group at this rather difficult time," he said.
"They have also expressed their deep concern ... at the circumstances which forced me to stand down as president."
Mr Jones was forced to resign as leader of Plaid Cymru after his party's poor performance in the Welsh assembly election.
The dramatic announcement shocked his party, a week after Plaid suffered major losses in the poll and half the 12 Plaid assembly members said they wanted him to go immediately.
It provoked angry recrimination within the party - one Plaid MP said he was disgusted the AMs moved so quickly, and failed to consult anyone outside the assembly.
There were also accusations of a plot to oust Mr Jones, led by the mid and west Wales AM Helen Mary Jones.
Mr Jones was born in Denbigh in 1949, and educated in Pontardawe and Liverpool.
He was a solicitor before becoming MP for Ynys Mon in 1987. He gave up his seat at Westminster at the last general election to concentrate on his role as assembly member for the same seat.
He took over as president of Plaid Cymru in summer 2000, replacing Dafydd Wigley, who had led Plaid to its greatest success at the first assembly elections.
But health problems forced Mr Wigley to stand down, and Mr Jones was elected with a thumping 77% of the vote.
A minister's son who is regarded as a Plaid Cymru moderate, he fought off two left-wing candidates in 2000.
As the new leader of Plaid Cymru in the Welsh assembly, his challenge now will be to heal those rifts as well as reclaim the seats that were lost during the election in May.