BELFAST, Northern Ireland (CN) — A man leans out of a window high up on the hulking parliament building of Northern Ireland and shouts to a gaggle of journalists down below. “Get me a united Ireland or I jump!” It was a joke, but one full of meaning.
That man was Gerry Adams, the leader of Sinn Féin, the political wing of the Provisional Irish Republican Army, the paramilitary group that killed about 1,771 people in its ruthless quest to end British rule in Northern Ireland, a state carved out of Ireland in the 1920s as a home for Protestants.
The context for the joke was historic: Adams and other politicians representing Roman Catholics had just resumed sitting in Northern Ireland's parliament on equal footing with Protestants, thanks to the Good Friday Agreement in 1998 that ended decades of bloodshed.
The message was clear: Despite having obtained political equality with Protestants in Northern Ireland, Sinn Féin was still beholden to the idea of driving the British out of Ireland.
Twenty-one years later, the campaign to unify Ireland is being revived by the combustible Brexit referendum, and it's a cause bolstered by a slow transformation taking place in Northern Ireland as the Protestant-majority country changes into a place where Catholics appear set to become the majority. It's possible that Catholics will outnumber Protestants in the next census in 2021. This new arithmetic played out in the last parliament elections in 2017: For the first time, Protestant political parties lost their majority.
In Belfast, many Catholics exude a sense of confidence that one day in the not-so-distant future they will be living in the Republic of Ireland rather than in the United Kingdom.
“The demographics are changing the country,” said Joseph Flynn, the 61-year-old owner of a hardware store in the Catholic stronghold of Falls Road in West Belfast.
“It will happen,” he said about unification. “It's only a matter of time. This here [Brexit] will only speed it up. There's nothing for Ireland in this whole Brexit.”

Northern Ireland is also a country where Sinn Féin — once a small party viewed as the repugnant public face of IRA gunmen and bombers — has grown into the dominant political force among Catholics and those who are pro-Irish.
In parallel fashion, Sinn Féin's main political rival is an equally radical Protestant party whose goal historically has been to limit the power of Catholics in government in Northern Ireland: This is the Democratic Unionist Party. Like Sinn Féin, the DUP was formerly a small party and viewed as a menace to peace.
The two parties now are fighting over this big question facing Ireland: Should Northern Ireland exist at all? Should it become part of an Irish federal or republican state? Should it remain part of the United Kingdom?
After the United Kingdom voted to leave the European Union in the 2016 Brexit referendum, the contentious question of Irish unity sprang back with energy into the political discourse.
Why? Because a majority of people of Northern Ireland voted against leaving the EU: 56 percent were in favor of staying. Polls show support for Irish unity growing since Brexit.

The day after the Brexit vote, Martin McGuinness, a former IRA commander and Sinn Féin leader in Northern Ireland's parliament, re-awoke the sleeping issue of holding a unification referendum, known as a “border poll” because it would ask people if they want to remove the U.K.-Irish border.
“I think that our case for a border poll has also been strengthened by the outcome of this vote,” he told journalists. He said that Brexit undermined the Good Friday Agreement.