THE murder of Det Garda Jerry McCabe in Limerick by a militant IRA unit and attempts by a Sinn Fein cumann in Cork to challenge the party's acceptance of the Mitchell principles present dilemmas to the republican leadership it could have done without.

When Mr Gerry Adams leads his party team to Stormont Castle today and demands entry to negotiations, he wants to present a strong, united front. Any political or military dissidence weakens his standing.

If the Sinn Fein president cannot control his party or keep the IRA in line, his prestige as a negotiator is greatly weakened. Both governments the SDLP, and even the unionists" know he is walking a tightrope to bring the republican movement from its traditional hardline position, towards a compromise settlement.

So far, despite the Limerick and, Cork events, he is keeping his balance. Sinn Fein has been allowed to circumvent Det Garda McCabe's murder. A weekend ard chomhairle statement made no reference to it and the Government is not pushing the issue.

The republican leadership would like to deal assertively with the Munster unit which carried out the attack. But it knows that would exacerbate internal difficulties. Harsh disciplinary action against those involved could magnify the problem and caused other dissidents to strike out in sympathy.

The republican movement is a large, diverse body whose membership varies greatly in its support for the peace process. IRA activity in Limerick and Sinn Fein activity in Cork reflect discomfort among a section of grassroots with the compromises that the movement has made in the name of peace.

But the leadership is still setting the agenda and the overall thrust is towards constitutionalism. The exact timing of a renewed IRA ceasefire remains uncertain but its likelihood does not seem in doubt.

Sinn Fein's impressive electoral success has greatly strengthened the hand of moderates in the movement. Militants are finding it almost impossible in the short term to reverse, that trend.

Before the election result, the leadership was under pressure. The peace process was moving too slowly for the grassroots. Disillusionment was widespread. Sinn Fein's record 15.5 per cent breathed new life into the unarmed strategy.

Mr Adams can truthfully say to hardliners that Sinn Fein will poll only half as well if the war returns. He can state that his strategy has brought political rewards from the electorate if not from the British government.

The Cork cumann is calling for a special ard fheis to discuss the party's recent endorsement of the Mitchell principles. But at least one third of Sinn Fein cumainn must agree to the move and that support seems lacking. Mr Adams still has the trust of the mass of rank and file.

He is currently insisting his party's electoral mandate warrants entry into all party talks today regardless of what the IRA does. He knows that is not on the cards. But Sinn Fein will play the victim to the hilt for PR purposes.

It plans a protest extravaganza if it is locked out of the talks at Stormont Castle today. The arrival of the US cavalry, in the form of Senator George Mitchell, to chair the talks, will lead to the eventual reinstatement of the ceasefire, sources say. It's one thin to mess with Downing Street, quite another to wrestle with the White House.

An officially renewed ceasefire would not be warmly welcomed by the average IRA member but the election result - and the impression that republicans are going somewhere means they could live with it.

Dissidents within the movement who had hoped Sinn Fein's vote would collapse - thus forcing a change of strategy know that they have currently lost the initiative.

Leading members of the IRA's Belfast Brigade and GHQ staff who have gone along with the peace process were present at the City Hall count and appeared delighted with the poll. But it will ultimately weaken even their role in the movement.

Few of Sinn Fein's 116,000 votes 38,000 up on the 1992 general election were for the Provos. Most, were for the peace strategy. Mr Adams is no longer just the leader of the IRA's political wing; he now has his own independent mandate.

Maintaining that new support (most of which came from former SDLP voters) will inevitably demand a further moderation of the party's traditional militancy. It will be difficult to do this without alienating supporters in the ghettos.

So far, no credible alternative exists to the Provos in working class, nationalist areas. Republican Sinh Fein and the Irish Republican Socialist Party, the INLA's political wing, have failed to make an impact.

A section of young nationalists still has no interest in constitutional politics. After the polls closed in Derry, 500 youths petrol bombed the RUC.

It is dangerous that republican hopes are so high. The joint SDLP Sinn Fein vote was only 37 per cent. Nationalists are not in a position to dictate the terms of any settlement.

And grassroots republicans should know from the hunger strike that electoral victory does not necessarily achieve their goals. In 1981, Bobby Sands won 30,000 votes to become MP for Fermanagh and South Tyrone. In a widely hailed "success" last week, Sinn Fein managed only a third of that total in the constituency.

If 30,000 votes did not save Bobby Sands's life, 11,000 in the same place will not secure a settlement which meets republican demand.

The Sinn Fein members who oppose acceptance of the Mitchell principles and the IRA members who murdered Det Garda McCabe might not be satisfied with that settlement.

Hardline republicans have not gone away. But they have been relegated to the sidelines. Mr Adams will be doing everything in his power to censure that they remain there.