Labour will be forced out of power in the Welsh assembly soon by a coalition of opposition parties, a leading Plaid Cymru figure has predicted.
Rhodri Morgan leads a minority Labour government in the assembly
Dai Lloyd, chair of the Plaid AMs, said they would not wait "months and months" to oust First Minister Rhodri Morgan.
Dr Lloyd spoke after a Liberal Democrat U-turn rekindled a "rainbow alliance" with Plaid and the Conservatives.
Assembly Lib Dem leader Mike German said he had no idea how long the deal would take, but wanted to deliver it.
Mr Morgan was reappointed to Wales's top post last Friday after the coalition agreement between the three other parties appeared to have collapsed when it was rejected by the Lib Dems.
But the following day Lib Dems voted again, this time to go ahead with the alliance.
Labour has a minority government, with 26 of the 60 seats, and if the other parties unite, they can remove Mr Morgan with a vote of no confidence.
Dr Lloyd told BBC Radio Wales that an "historic opportunity" had been missed when the Lib Dems had initially "caved in" over the opposition deal.
"We've all agreed on this programme for a Plaid-led government, but basically we have to await our opportunities, and push for a vote of no confidence now when an issue of sufficient magnitude rears its ugly head," he said.
Dr Lloyd told Good Morning Wales that his party had been "shattered at the destruction of the vision of a Plaid Cymru-led government" when the Lib Dems had "bottled it".
But he said the opposition would "await our opportunity now for Labour to mess up big time".
"We shall be doing it (ousting Labour) but the reality is we have a minority Labour administration in power now. We have to trigger a vote of no confidence.
"There are plenty of opportunities because Labour's programme is hardly visionary.
Plaid leader Ieuan Wyn Jones would be first minister in a coalition
"We've stood by awaiting eight years of change. Basically Labour have under-achieved and failed Wales over the last eight years.
"I can't imagine us hanging around for months and months before we trigger a no confidence vote."
Four Plaid AMs have come out against coalition, and before any deal is agreed it will have to be approved by the party's ruling body. The Plaid national council is expected to meet in July to discuss it.
Dr Lloyd said: "We have internal differences of opinion but Labour will not split us on this.
"At the end of the day, whatever discussions we have internally, the majority view will hold and the majority decision will hold.
"Because Wales has only two choices now: one of a Plaid first minister in a Plaid-led government or continually propping up a failed Labour administration.
Dr Lloyd said Mr Morgan would be "as tribal as Labour have always been, trying to do the best for Labour only, as opposed to a Plaid Cymru-led government - even though it might be difficult - doing the best for all the people of Wales."
Lib Dem Mike German said: "The wheels came off the wagon earlier in the week but we put the wheels back on very decisively on Saturday."
Mr German said the opposition had to take time and reflect on the decision, but the "key thing" was the programme for government the parties had put together.
"We need to work on that now during the coming weeks, but it's also important that we deliver that programme."
Mr German's own position has been questioned by some in his party, and he said: "One thing you can say about me I think is that I'm prepared to take the tough decisions, take the rough and the tumble... but in the end to do the right thing for the people of Wales.
"And what I think is right here is the decision my party took and that's what I intend to try to deliver."