EU immigrants are having one of their first chances to vote since the Brexit referendum as local elections take place in London and other parts of the UK.
The elections only concern local government and have no impact on the make-up of MPs in the national parliament.
Nevertheless they are expected to provide a gauge of the popularity of Prime Minister Theresa May and her government.
It comes as May is facing a possible revolt over her Brexit strategy and a scandal over immigration policies that has already forced one high-level resignation.
"Winning elections keeps people together, losing causes dissent. Conservatives will need to avoid the ill-discipline of fighting like ferrets in a sack," said Rob Wilson, a former Conservative MP, writing for the party's grassroots website ConservativeHome.
More than 40% of council seats up for election today are in London, which voted against leaving the European Union nearly two years ago.
Other local authorities elsewhere in the country are only electing a third of their councillors this time around.
It will also be a chance for EU immigrants — upset over uncertainty around whether they will retain the same rights as they have now post-Brexit — to vote.
The headline-grabbing results in the capital are forecast to see a swing toward the opposition Labour Party, reinvigorated under socialist Jeremy Corbyn and fighting a campaign focused on the effects of eight years of Conservative-led spending cuts.
A Survation poll on Wednesday in London showed Labour 20% points ahead of the Conservatives.
May's party could lose control of some of the eight London boroughs it currently runs out of 32 in total.
This would reflect both weariness over cutbacks that affect citizens' daily lives and broader issues like Brexit and the treatment of migrants.