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."
The MPs' endorsements come ahead of the first of eight leadership hustings for party members, with the first held in Pontypridd on Tuesday night.
The result of Plaid Cymru's leadership election will be announced on 28 September.