Former US senator Gary Hart is due in Northern Ireland to meet representatives of the main parties at Stormont.
The 77-year-old was asked to make an assessment of the peace process by US Secretary of State John Kerry.
Until he got into a controversy about his private life in 1987, he was the frontrunner for the Democratic presidential nomination.
More than two decades later, he is often talked about as one of the best president's America never had.
His counsel is often sought: in that context. His friend of many years, the current US Secretary of State John Kerry, has asked him to take the political temperature in Northern Ireland.
Mr Hart, who is on a fact-finding mission, had meetings in London on Tuesday.
He was in Dublin yesterday where he held talks with Tánaiste Joan Burton and Minister for Foreign Affairs Charlie Flanagan.
His itinerary in Belfast today will involve meetings with representatives of all the main parties at Stormont.
This will include Sinn Féin's Martin McGuinness, the Deputy First Minister.
Peter Robinson of the DUP is on annual leave so the party will be represented by Nigel Dodds.
However, this is not the start of a Haass 2 arrangement.
Richard Haass, the US diplomat who chaired failed political negotiations last year, had been invited in by the first and deputy first ministers.
Mr Hart's presence is a sign of interest, and possibly concern by the US administration.