The final votes push is under way ahead of next Thursday's crucial council and European Parliament elections amid indications that Labour and Tories are neck and neck.
This will be a nationwide test, with the booths open throughout the UK for the EU battle in addition to balloting for 161 English local authorities and those in Northern Ireland.
The Press Association's survey of by-elections between Budget week and May 8 suggested a knife-edge lead for Labour, which has been confirmed by opinion polls.
The local seats up for election this year were last fought in 2010 on the same day as the general election. With Prime Minister David Cameron due to go to the country next May, the results will be closely scanned by party chiefs and pundits.
The focus in the European polls is the performance of Nigel Farage's Ukip. It is hoping to build on a strong showing last time to challenge for first place.
Even if Labour's poll lead has shrunk, it should be confident of making some seat and council control gains. The biggest battlefield is in the London boroughs, where all seats are up for grabs.
Possible Labour targets are Tory marginals at Croydon and Barnet, and Merton, which is under no overall control.
Conservatives may take Kingston-upon-Thames from Liberal Democrats and Redbridge, currently under no outright control.
But Tories could come under pressure from Lib Dems at Richmond. Two councils have already shifted control as a result of councillor defections, from Labour at Harrow and Tory at Havering.
Outside the capital most of the elections involve about a third of the seats. In the conurbations, Tories are fighting to defend their two metropolitan authorities at Trafford and Solihull.
Possible Labour targets are Walsall and Calderdale. Liberal Democrats will want to make progress at Stockport where they are the largest party.
District councils where Labour has control-gain hopes include Amber Valley and West Lancashire from Conservative and Cambridge from NOC.
Tories could lose overall power at Purbeck and Tamworth. Conservatives' chances of gains may include Basingstoke and Deane and St Albans as well as Winchester, which is also a Lib Dem target.
West Oxfordshire which has the same boundaries as Mr Cameron's Witney constituency, would still stay under Tories' control even if they lost all 13 seats they are defending this year. But there will be interest in any inroads by other parties, particularly Ukip.
In the unitary authorities, Tories face possible defeat at Southend-on-Sea.They might be in danger at Swindon where they have a one-seat majority, although the previous election was in 2012 when Labour was riding high.
An all-out election at Milton Keynes opens the way to Labour hopes but the party will have a tough fight to hold on at Thurrock.
In the European elections, Ukip will seek to take centre stage.
A first place for the party, in a battleground fought on its favoured grounds, would be a blow for the major party leaders - particularly Mr Cameron, who could ill afford an internal Tory party war over Europe in the general election run-up. Some opinion polls have already hinted at a strong Ukip performance.
T he Green Party also has a tradition of punching above its weight in European elections. It may hope for a boost from its opposition to fracking.
Candidates, council staff and journalists face a five-day election marathon.
Polling stations are open all day on Thursday. Some councils will count overnight but many will declare during Friday.
There is the possibility that the process will spill over into early Saturday morning.
Counting of the European Parliament votes starts on Sunday but no announcements can be made until 10pm under rules barring declarations until polls have closed all over the EU.
Final results in Scotland will not be available until Monday morning, because of opposition to Sunday working in Comhairle nan Eilean Siar - Western Isles.
But - at the same time - counting will be getting under way in Northern Ireland. This will be under the single transferable vote system, possibly involving several rounds.