Democratic Unionists 'in spotlight'
The resignation of senior Democratic Unionist Jim Wells from his ministerial portfolio after comments about child abuse and gay relationships comes at a pivotal moment for the DUP's fortunes at Westminster.
The party founded by fundamentalist preacher the Rev Ian Paisley could be coming of age as a kingmaker in a hung parliament - where its up to 10 votes will be much sought after.
David Cameron has said he will "never validate" the DUP's position on gay rights, and Nick Clegg said some of their views were "backwards".
But with the race between Britain's largest parties neck and neck, it is unlikely to be a deal breaker.
The DUP are no strangers to controversy over their strongly held stance on gay issues - leader Peter Robinson's wife Iris once called for homosexuals to seek psychiatric counselling.
The party has repeatedly refused to authorise same sex marriage and has unyielding, principled moral positions opposing abortion. Many of its members espouse traditional Christianity in the form of the Free Presbyterian Church.
DUP leaders said they have a "plan" for coalition - seeking protection of front line public services. The party has also sought a slowing in the rate at which the budget deficit is cut.
The party was adamantly opposed to Scottish nationalism and supports measures to keep the UK united as well as a referendum on EU membership.
It is likely to seek concessions on loyal order parading as part of any post-poll negotiations.
But a party forged during the Troubles in opposition to any form of compromise with the IRA remains deeply suspicious of separatist nationalism - although its support for parades and the display of the Union flag clearly exhibit British identity.
Deputy leader Nigel Dodds has said the Conservatives' "English votes for English laws" plan would create a constitutional mess and fuel nationalist paranoia.
The DUP has agreed a pact in four marginal seats - Belfast North, Belfast East, Newry and Armagh and Fermanagh and South Tyrone - with its Ulster Unionist rivals in an attempt to return the most unionist seats to Westminster by one or other standing aside and giving the other a clear run in the constituencies.
It is an old tactic decried by nationalists as sectarian, yet Sinn Fein was quick to offer a retaliatory arrangement with the SDLP - ultimately rejected.
Fermanagh and South Tyrone is the UK's most marginal seat, Sinn Fein's Michelle Gildernew first won the constituency she has held for 14 years - but last time a court ruled she had won by just one vote.
Sinn Fein does not take seats at Westminster as part of a republican abstentionist policy dating back decades, and rumours of a deal with Labour were quickly quashed.
Deputy First Minister Martin McGuinness was among the first to call for Mr Wells to resign after he said a child brought up in a homosexual relationship was far more likely to be abused and neglected.
DUP leader Peter Robinson has said his party colleague knew his comments were wrong and urged people to "give him a break".
Sinn Fein and the DUP are unlikely to reach common ground over same sex marriage, but they remain united on one central issue - the need for more money from London to boost Northern Ireland's fragile economy.