Uneasy lies the head that wears a crown, moaned Shakespeare's Henry IV, proclaiming a fact of political life that holds as true today as in the 15th century.
That's why Peter Robinson has been at such pains to assure us he will not be standing down as First Minister or leader of the DUP.
Mr Robinson has led his party to unprecedented electoral success, but that does not make his tenure any more secure. The same could be said of the man who has been cast as his direct political opposite.
Gerry Adams made Sinn Fein the dominant nationalist voice in Northern Ireland. He then switched his attention to southern politics and has taken the party to a point where, on opinion poll figures, it seems a shoo-in for a place in the Republic's next government.
So, when Sinn Fein met in Carlingford last weekend for a planning conference ahead of the new Dail session, Mr Adams should have been enjoying acclaim.
Instead, he was fending off media questions about his leadership and whether he might be replaced by the Dublin TD Mary Lou McDonald, or the Donegal deputy Pearse Doherty.
Like Mr Robinson, he is determined to remain at his post. "I will certainly lead the party into the next election,'' he declared in a recent interview.
On the face of it, that should also mean leading Sinn Fein into government. Some opinion polls have made it the Republic's second most popular party, behind Fine Gael and ahead of Fianna Fail.
All polls put it well ahead of Labour, current junior partners in the government coalition.
Austerity measures have caused a drastic slump in support for Labour and the party will do well to retain half the 37 seats it won at the last election.
Austerity goes down much better with middle-class Fine Gael voters but, while Enda Kenny's party would undoubtedly top the poll in an election held now, it is unlikely to improve on its 2011 showing and will probably lose some of the 76 seats it won then.
So Labour's seats might not be enough to get Kenny back into government next time around – even if Labour members are prepared to risk another coalition.
On opinion poll figures, Sinn Fein could double its present tally of 14 seats, making it a strong candidate for the role of junior coalition partner and ticking one of the boxes on Mr Adams's wish-list – that he and his party should be in government for 1916 centenary celebrations.
This would present huge problems for Fine Gael. The party of law and order has always kept Sinn Fein at arm's length and remains repelled by its terrorist past – ironic for the heirs of Michael Collins you might think, but successful politicians rarely do irony.
What they do is pragmatism and, if forced by the electoral figures, Mr Kenny might just be prepared to close his eyes and broker a deal with the fragrant Ms McDonald or the clean-cut Mr Doherty.
But the thought of sharing a 1916 platform with the man who denies he was an IRA leader is not one Kenny would contemplate.
He recently challenged Mr Adams to "come clean'' on his IRA membership, comparing him unfavourably with Martin McGuinness.
"I had a serious discussion with Martin McGuinness... and he was forthright enough and honest enough to admit that he was a member of the IRA,'' said the Taoiseach.
"Gerry Adams might like to make a statement about that. From all the evidence that I've read and all the evidence I've heard, my belief is that he was a member of the army council of the IRA.
"When Deputy Adams says to me that he wants a truth and reconciliation commission... I'd like him to be absolutely truthful about this.''
That does not sound like a man who will be pulling up a chair at the cabinet table for Mr Adams anytime soon.
And it is not only the past that drives a wedge between Mr Kenny and Mr Adams. Their parties are poles apart on the economy, too.
Sinn Fein, with economic policies that range from left-of-centre to neo-Marxist, has constantly urged the Republic to default on its debts, particularly those run up by banks.
Fine Gael, most of whose TDs could sit comfortably on the Conservative benches at Westminster, has been the chief advocate of the tough measures which appear to be pulling the country back to the black.
Such apparent incompatibility does not rule out a deal. There have been many strange bedfellows in Irish politics.
But it does seem to rule out a deal with Mr Adams, whose grasp of economic matters always appears shaky and has been shown to worry voters.
His poor performance in an RTE interview before the 2011 election is thought to have cost the party votes.
Would Ms McDonald or Mr Doherty do any better in government? Maybe not.
But they might be given the chance – which is more than can be said for Mr Adams.
So, uneasy lies the head. For, as Shakespeare also said, "faithful friends are hard to find''.