The Irish nationalists now have seven MPs but they have historically refused to attend the Westminster parliament.
A deal could have huge implications for Brexit and politics in Northern Ireland.
This is not the first time a Westminster government has needed support from unionists.
Theresa May is to rely on support from Northern Ireland's biggest party in order to survive as a minority government. But that help doesn't come for free.
The two main parties in Stormont still haven't reached a power-sharing deal, and a national vote is unlikely to help matters.
Violent dissident republicanism is still making its presence felt.
Time is running out for a compromise agreement between the two main parties at Stormont.
The former deputy first minister was once a feared IRA sniper but became a central figure in the move towards peace.
The DUP and Sinn Féin face direct rule if they can't agree on a programme for government.
The two ruling parties live by the letter of the Good Friday Agreement, but not the spirit.
What was already an uneasy alliance first turned sour, and then utterly disintegrated. Where did it all go wrong?
A political scandal has laid bare the irreconcilable differences between to two main parties in the power-sharing agreement.
A surprising level of anti-EU sentiment among unionists should be on Remain's radar.
After months of deadlock, the DUP and Sinn Féin have settled some of their issues – but they've kicked the hard stuff into the long grass.
First minister Peter Robinson has resigned, casting uncertainty over the future of power sharing.
Stormont's parties refuse to conduct politics in any mode besides crisis mode.
Some people's dreams just came true in Northern Ireland – but did the UK-wide result shatter them?
Experts provide a rolling response, live as the results come in for the 2015 general election.
Losing seats but gaining power is likely to be an apt title for any book written about the Lib Dems 2015 election experience.
In 2010, there were more than 1,000 potential coalition options. Here's how to make friends in 2015.