Updated

Voters in Northern Ireland were challenged Thursday to back renewed power-sharing between their Protestant and Catholic leaders, an experiment in compromise designed to end decades of bloodshed over the territory's future.

The re-election of the Northern Ireland Assembly follows a surprisingly successful full four-year term for its outgoing coalition of British Protestants and Irish Catholics, who spent more than three decades locked in conflict that cost more than 3,700 lives.

Such cross-community cooperation was the central goal of Northern Ireland's Good Friday peace accord, but it faces a resurgent campaign of attacks by Irish Republican Army dissidents determined to wreck the peace. At the start of campaigning a month ago, an IRA splinter group killed a young Catholic police recruit with a booby-trap bomb under his car.

The family of the victim, Constable Ronan Kerr, issued an eve-of-election appeal for all 1.2 million registered voters to cast a ballot as the best answer to his killers.

"By not voting, we are giving the men of violence control and power over our lives. By exercising our democratic right to vote, we are condemning violence, ensuring power-sharing and mutual respect, and supporting law and order in our country," said the statement from the dead officer's mother, brothers and sisters.

The Assembly's 108 members wield the power to appoint the next coalition government. Results will be announced Friday and are expected to reaffirm the dominant positions of the two current largest parties: the Catholics of Sinn Fein, and the Protestants of the Democratic Unionists.

The Democratic Unionists, built on a foundation proclaiming eternal opposition to Sinn Fein, stunned the world in 2007 by agreeing to share the same Cabinet table with the IRA-linked party.

They were responding to the IRA's 2005 decisions to disarm and renounce violence and Sinn Fein's 2007 acceptance of the legal authority of the Northern Ireland police — commitments designed to reassure the Protestant majority that the IRA's 1970-1997 campaign of bombings and shootings would never resume.

In a bid to wreck the coalition, several IRA splinter groups have been ramping up attacks. They killed two off-duty British soldiers and a policeman in 2009, detonated a half-dozen car bombs last year that killed nobody, then killed Kerr April 2.

The violent challenge has served only to draw the power-sharing leaders closer together. The IRA dissidents' affiliated politicians are boycotting the election in an acknowledgment of their unpopularity.

The Democratic Unionist leader of the government, Peter Robinson, and his Sinn Fein colleague, former IRA commander Martin McGuinness, demonstrated their exceptional solidarity during televised campaign debates that underscored the dramatically changed political landscape of Northern Ireland.

"I believe the people of Northern want us to work together," Robinson said during the last TV debate of the campaign this week, with McGuinness sitting beside him.

"I think our people actually like to see us working together," McGuinness said to audience applause.

Their main rivals for votes — the Protestants of the Ulster Unionists, and the Catholics of the Social Democratic and Labour Party (SDLP) — long led calls for peace and power-sharing, but today struggle for relevance now that the two hard-line parties have stolen their script.

In 2007, the Democratic Unionists won 36 Assembly seats, Sinn Fein 28. The Ulster Unionists won 18, the SDLP 16. That result meant the Democratic Unionists won five posts in the administration and installed Robinson, the party leader, as government leader. Sinn Fein received four posts, the Ulster Unionists two, and the SDLP one.

A fifth party, the middle-of-the-road Alliance Party, joined the coalition last year so that its leader, David Ford, could become Northern Ireland's new justice minister. That move completed the most difficult challenge facing the new government — to take responsibility for the province's law-and-order systems from Britain.

This means that no significant political party sits in opposition in Northern Ireland's Stormont parliament, a strange condition for any democracy.

One small party of Protestant hard-liners, Traditional Unionist Voice, is campaigning to end cooperation with Sinn Fein and could score a breakthrough in a few districts.

"We want to shake up Stormont. Stormont at least needs an opposition," said Traditional Unionist Voice leader Jim Allister, a former Democratic Unionist lawmaker who defected when his party agreed to cooperate with Sinn Fein.

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Online:

Democratic Unionists, http://www.dup.org.uk/

Sinn Fein, http://www.sinnfein.ie/

Northern Ireland Assembly, http://www.niassembly.gov.uk/