As we enter the last full week of campaigning for the National Assembly election, Labour retains a clear lead in the latest Welsh Political Barometer poll. But its support has slipped to the lowest seen for six years. Meanwhile the poll contains some encouragement for both Plaid Cymru and even the possibility of good news for the Welsh Liberal Democrats.

Those are the headline findings from our new poll, conducted by YouGov between 19-22 April. The poll once again asked a representative sample of people in Wales about their voting intentions on both the constituency and regional ballots for the National Assembly election. Here are the figures for the constituency vote (with changes on the previous Welsh Political Barometer poll, conducted at the beginning of the month, in brackets):

Labour: 33% (-2%)

Plaid Cymru: 21% (no change)

Conservatives: 19% (no change)

UKIP: 15% (-2%)

Liberal Democrats: 8% (+2%)

Others: 3% (no change)

So here we see Labour remaining well ahead of the field, despite its support slipping two points since the previous poll. Plaid Cymru will be encouraged that they retain a clear second place ahead of the Conservatives; while the Tories can hardly be pleased by these results, the decline in support for UKIP at least means that, unlike in our previous poll, they do not appear under threat of falling into fourth place. And, for the first time in a long while, the poll also contains some encouragement for the Welsh Liberal Democrats: their two point rise here comes on top of a further slight increase in the last poll.

Applying uniformly across Wales the changes since the 2011 National Assembly election indicated by this poll, the figures project three constituency seats to change hands. The Liberal Democrats are projected to capture Cardiff Central from Labour; meanwhile Plaid Cymru are projected to gain Llanelli from Labour and also Carmarthen West & South Pembrokeshire from the Conservatives.

For the regional list vote, the figures in our new poll are as follows (with changes from the last poll again in brackets):

Labour: 29% (-2%)

Plaid Cymru: 22% (+2%)

Conservatives: 19% (-1%)

UKIP: 15% (-1%)

Liberal Democrats: 8% (+3%)

Greens: 4% (no change)

Others: 4% (+1%)

Again assuming uniform swings since the 2011 election across Wales, and after taking into account the distribution of constituency seats, this gives us the following projected distribution of the regional seats:

North Wales: 2 UKIP, 1 Conservative, 1 Plaid Cymru

Mid & West Wales: 2 Labour, 2 UKIP

South Wales West: 2 Plaid Cymru, 1 Conservative, 1 UKIP

South Wales Central: 2 Conservative, 1 Plaid Cymru, 1 UKIP

South Wales East: 2 Plaid Cymru, 1 Conservative, 1 UKIP

Combining both sets of figures produces the following overall outcome for the National Assembly:

Labour: 28 seats (26 constituency seats + 2 list seats)

Plaid Cymru: 13 seats (7 constituency seats + 6 list seats)

Conservatives: 10 seats (5 constituency seats + 5 list seats)

UKIP: 7 seats (7 list seats)

Liberal Democrats: 2 seats (2 constituency seats)

Labour thus remain some way ahead of the field. But they must be somewhat concerned that support has edged downwards further: 33% on the constituency vote is Labour’s lowest level in any Welsh poll since before the 2010 general election. A similar YouGov poll conducted in late April 2011 put Labour on 45% for the constituency vote and 41% for the list vote. So Labour are now twelve percentage points lower, on both ballots, than they were at this stage in the electoral cycle before the last Assembly election. Were Labour’s election performance this year to fall below their poll rating – which it has normally done in Wales in recent years – then Labour could be on course for their worst ever vote share in a National Assembly election.

And yet the divided opposition leaves Labour well in the lead. Plaid Cymru must be encouraged that this poll now has them in a clear second place on both ballots, and projected to finish three seats ahead of the Conservatives. Plaid would need to make further progress, or achieve very strong local swings in particular constituencies, to make substantially greater seat gains. Nonetheless, given that they have run behind the Conservatives on both Assembly ballots for most of the last five years, recent trends are encouraging for them. The findings are much more concerning for the Conservatives; the optimistic talk at the party’s March Welsh conference of making significant seat gains now appears significantly less likely to be realised.

Meanwhile, for the first time in a very long while the fourth party in the Assembly, the Liberal Democrats, have some moderately good polling news. This poll suggests that the Assembly election campaign has enabled them to increase their support levels. Their position is still highly precarious, but the 8% they score on the list vote here is equal to their vote share in 2011, and suggests that they may just have a chance of holding onto some of their current regional list seats. Meanwhile UKIP have seen their support slip slightly in this poll. But unless they suffer a further substantial erosion in support, they are still likely to win regionalist list seats on May 5th across most, if not all, of Wales’ five electoral regions.