Plaid Cymru leader Leanne Wood has failed to win any support from her Westminster MPs, with most endorsing her rival Adam Price in the party's leadership contest.
Liz Saville Roberts and Hywel Williams have announced they have joined Jonathan Edwards in backing Mr Price.
With Ben Lake supporting Rhun ap Iorwerth, it means all four Plaid MPs are seeking a change in leader.
Leanne Wood said she expects the party to unite behind whoever members choose.
Ms Wood is fighting for re-election after Adam Price and Rhun ap Iorwerth triggered a contest earlier in the summer.
In a joint statement announcing their endorsement of Mr Price, Ms Saville Roberts and Mr Williams said: "We are proud that our party has people of such calibre as the three candidates.
"Undoubtedly the other two have a further huge contribution to make.
"But in a period of such tumult and danger for our nation we believe that it is Adam who has the outstanding vision and the ability to lead."
Plaid Westminster leader Liz Saville Roberts is MP for Dwyfor Meirionnydd, while Mr Williams is MP for Arfon.
Meanwhile former MP and leader in Westminster Elfyn Llwyd backed Rhun ap Iorwerth's run for the leadership on Monday.
Two AMs are known to have backed candidates - Dai Lloyd is supporting Ms Wood, while Llyr Gruffydd is backing Mr Price.
Ms Wood's campaign said she has won endorsements from more than 50 county councillors, as well as Arfon Jones, police and crime commissioner for North Wales.
Ms Wood said: "The grassroots members decide on the leader and it's up to the elected members to get behind the democratically chosen leader. I expect the party to unite behind whoever the membership choose."
Analysis by BBC Wales political correspondent Daniel Davies
There are near enough 8,000 members of Plaid Cymru.
Everyone's vote carries the same weight, so would four politicians be decisive in the outcome? Probably not.
But nevertheless, they will want to avoid splits. There have been rumblings and tension between Leanne Wood and some in Westminster in recent months.
If she carries on, she will want to do something about that. No wonder she put out a statement saying whoever wins, the party will have to unite behind the leader.
The MPs' endorsements followed an ITV Wales debate between the three candidates.
Adam Price told the Sharp End programme that any opportunity to stop Brexit should be taken.
"The Party of Wales has to put the interest of Wales first. The people of Wales won't forgive us unless we are absolutely clear about the consequences of Brexit for the Welsh economy," he said.
But while Leanne Wood backed a final vote for the public on any Brexit deal, she said: "What we are seeing is a political context where the far right are on the rise, and all they don't have is a grievance.
"We have to be very careful that we don't give them that grievance or we could be in very dangerous, difficult political territory."
Rhun ap Iorwerth described himself as a "passionate pro-European" and said the referendum should have been a two stage vote.
"One on the principle", he said. "But a second one on the practice of what it actually means."
Plaid will hold eight leadership hustings for members, with the first taking place in Pontypridd on Tuesday.
The result of Plaid Cymru's leadership election will be announced on 28 September.