Leanne Wood faces being challenged for Plaid Cymru leadership, unless she agrees to share the job.
In a highly critical intervention, Adam Price said the party had resorted to "predictable, plodding politics" and needed "press the reset button".
Mr Price said a male and female co-leadership was needed if Plaid is to win the 2021 election.
Ms Wood has said she will stand down if she does not become first minister at the next assembly election.
Under Plaid rules a window to challenge for the leadership comes around every two years, with Assembly Members having until Wednesday (4 July) to step forwards to fight for the role.
Ms Wood has not faced a challenge since being elected leader in 2012, but in a damning article in the Western Mail, Mr Price slates the party's progress and strategy on independence, saying change is needed "badly" and "fast".
Another possible contender, Ynys Mon AM Rhun ap Iorwerth also says he is considering whether to stand.
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But Carmarthen East and Dinefwr AM, Mr Price, says simply ousting Ms Wood would "leave a toxic residue of bitterness and recrimination" and instead sets out plans which would see Ms Wood stay in power, while sharing the role with a man.
"I have to say it's my view, and I believe that of many others in this great party, that we have generally failed to consistently articulate a comprehensive and compelling vision of the future," he writes.
"Our comfort zone has been a strange mixture of philosophical abstraction and the predictable, plodding politics of the parsimonious press release, the tired tweet and the formulaic Facebook status.
"Nowhere has this shallowness been more exposed than on the question of independence, our very raison d'être, where our failure to present a clear and persuasive exposition explains why we have lost more than a thousand of our eight thousand members in the last eight months.
"Pressing the reset button for our party has to start now; and it comes with the hard but vital work of developing a creative and credible body of ideas that will excite the interest and inspire the confidence of the people of Wales."
Mr Price writes that having a male and female jointly leading the party would give Plaid a "radical and powerful leadership that will avoid the traditional vulnerabilities of placing power in a single pair of hands.
"In our own party, co-leadership would allow us to embrace all viewpoints, to harness all drive and commitment for the widest political progress possible," he adds.
Also writing in the Western Mail, Mr ap Iowerth said: "I'm on the record saying I'm considering my response to Leanne's invitation for a debate on the leadership.
"What that means in reality is that I'm speaking to as many people as possible about how best to take Plaid Cymru forward. We're in this for Wales, not ourselves."
BBC Wales understands Mr Price would allow MPs as well as AMs to be elected co-leader, subject to a change in party rules.
It is understood that Mr Price wants Ms Wood to commit to his proposal a day before the deadline following discussions at a meeting of party AMs.
There has been mounting appetite within the party for a leadership challenge, with former Plaid leader in Westminster Elfyn Llwyd calling for a change in direction for the party and local constituency parties have called on both Mr Price and Mr ap Iorwerth to stand.
Meanwhile three AMs - Llyr Gruffydd, Sian Gwenllian and Elin Jones - have signed a letter calling for a competition.
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Days after denying he would challenge for the leadership Mr ap Iorwerth said now said he is "carefully considering" putting his name forward.
On Saturday 53 councillors from across Wales - who make up about a quarter of Plaid's councillors - pledged their support to Ms Wood to continue as leader.
Ms Wood has previously said she would welcome a leadership challenge.