Campaigners who fought for decades to end Northern Ireland’s same-sex-marriage ban and restrictions on abortion prepared on Monday for a momentous change to the laws on both at the stroke of midnight. Northern Ireland is the only part of the United Kingdom that does not allow same-sex marriage. Also, unlike England, Scotland and Wales, laws in Northern Ireland forbid abortion except where a mother’s life is at risk, bans that have been upheld by the region’s block of conservative politicians. But an overwhelming vote by British lawmakers in July to compel the government in London to overhaul the laws if Belfast’s devolved executive had not been restored by Oct. 21 is set to kick in with little or no hope of politicians ending the local parliament’s near three-year hiatus.