The Nova Scotia politician's future is the subject of much chatter on and around Parliament Hill in the wake of Baird's announcement Tuesday that he would resign his seat and move to something new.
When asked whether he would run in the next election, MacKay's response Wednesday was: "I filed my nomination papers, so I'm underway."
MacKay was acclaimed as the Conservative candidate in Central Nova last month.
But then, Baird had also been nominated in his Ottawa-area riding.
MacKay, 49, has been an MP since 1997. He ran successfully for the leadership of the Progressive Conservative party and then helped to facilitate a merger with the Canadian Alliance.
He did not run against Stephen Harper for the helm of the new party and went on to hold senior positions over the last nine years — foreign affairs, defence and justice.
He and Harper come from different parts of the Conservative family, but MacKay has carried out his leader's directives with little friction.
Through his time in politics, MacKay has nurtured a formidable group of political supporters who still regard him as a future party leader.
Would the time be right to move into the private sector and plan for a future leadership bid, as Brian Mulroney, Jean Chretien and others did in the past? Does it make sense to move on just before an election that is expected to see the party lose seats in Atlantic Canada?
MacKay has watched a parade of former colleagues, including Baird, Jim Flaherty, Jim Prentice, Stockwell Day and others, decide they've done their time and step down.
In 2009, MacKay was rumoured to be in the running for the job of NATO secretary general.
A Conservative source close to MacKay said he didn't have any reason to believe MacKay won't run again.
But there are diehard fans of the justice minister who think he should consider doing something else. Some who spoke to The Canadian Press on condition of anonymity said he would be smart to spend time in the private sector, given that he was only 31 when he was first elected.
Another point of view is that it makes more sense to stay in caucus just in case a sudden leadership race with tight timelines is called after the next election.
For now, MacKay appears to be prepared to stay and shepherd key law-and-order and security legislation through the House and Senate.
Said one Conservative close to MacKay: "His inbox is never empty, there's always something else that he wants to do."
Also on HuffPost