Liberal Democrat leader Sir Vince Cable has said he is "optimistic" about his party's future in Wales despite its wipe-out at the general election.
He said the Welsh Lib Dems would soon have "a new face" as their leader.
Sir Vince said the party would also benefit from having Kirsty Williams as "a source of strength" in coalition with Labour in the Welsh Government.
He was talking to BBC Wales as the Liberal Democrats' UK conference gets under way in Bournemouth.
Sir Vince told the Sunday Politics Wales programme Education Secretary Ms Williams was doing "a phenomenal job" and avoiding the mistakes the party made in coalition at UK level in ensuring that the public know about their "distinctive, positive" contribution to government.
The party lost its only seat in Wales, Ceredigion, at the election, and in the process lost its Welsh leader, Mark Williams.
Party members will next month elect his successor, who will no longer have to be either an MP or an AM.
Sir Vince said: "There is a lot of ground we have to recapture, I recognise that. I've been down to Wales twice in the last few weeks, but I'm optimistic.
"We have a strong, residual base, we have a long tradition of being active and strong in Welsh politics and the fact that Kirsty Williams is in the coalition government is a source of strength.
"She's achieving a great deal, getting a good result for students and aligning maintenance [grants] with the minimum wage, strengthening the pupil premium, she's achieved a lot.
"Actually it's one of the parts of the UK where we're actually in government and that's a positive."
The Lib Dems did so badly in June they lost their deposit - polling less than 5% of the vote - in 36 out of the 40 seats in Wales.
"The loss of Ceredigion in particular was a blow because Mark was a terrific MP," Sir Vince said.
"My job nationally at UK level is to try to build up our national vote share and, our people in Wales, we've got a sufficiently strong base good council groups in bits of south Wales, Swansea, Cardiff.
"We're very strong in mid Wales and there's a resurgence of optimism in north Wales, as I discovered when I met our members there.
"In the past we've had a quarter of the vote in Wales. We've gone down a long way from that but I think my job nationally is to build up the national messaging, the Liberal Democrats as a party of government, I'm there as a potential prime minister for the country and our Welsh colleagues will hopefully build on that platform."
Sir Vince was trade secretary in the Conservative-Lib Dem UK coalition between 2010 and 2015. The party lost 49 of their 57 seats across the UK and Sir Vince was asked what advice he would give to Kirsty Williams on how to handle coalitions.
He said: "The important thing when you're in a coalition government, you are part of a team. I had a major government department in the coalition government in the UK. I had eight ministers, two Lib Dems.
"You have to work in a team with people who are your political opponents but when you do something distinctive, positive, you've got to let the public know that this is the Lib Dem contribution. We perhaps didn't do enough of that when we were in the UK government and I know Kirsty is doing that very well in Wales."
A change in party rules means the new Welsh Lib Dem leader does not have to be an elected politician, only someone who has been approved to stand as a candidate for the Welsh Assembly or Westminster.
Sir Vince said: "It will be a new face and that is the way the party wanted to go. Kirsty is doing a phenomenal job but combining leadership with being a minister with a serious cabinet job in the Welsh Government, it was a burden she couldn't continue to carry.
"We've got a lot of talent, I've met a lot of them and I'm sure we will get good Welsh leadership. I've no problem with that."