Running as a Democrat, he must take this first step to add to his credentials for successive jobs in politics. He can’t win any statewide office because of his largely undiluted leftism and, outside of a judgeship which doesn’t seem to interest him, he can’t win any New Orleans-based post because he doesn’t identify as black (although the 1900 census lists his grandfather as black, and the 1880 census lists his great-grandmother, also notated as black on the same 1900 document, as mulatto.)
But his fealty to liberalism would make him competitive for his party’s presidential nomination. His eight years as mayor led to championing leftist causes at the expense of bread-and-butter concerns essential to running a city well: letting police resources dwindle while New Orleans festered as one of the most dangerous cities in the world; putting drainage matters on the back burner until crisis struck, having pretended to address these with administrative changes; or delaying resolution of issues costing the city money, such as until courts forced him to act on firefighter pensions or federal disaster relief money fell out of the skies to fund neglected road repairs.
Of course, that kind of record would make him uncompetitive against incumbent Republican Pres. Donald Trump, and party leaders would have less toxic alternatives that they see as more reliably extremist, but even an unsuccessful run would solidify his stature as a political heavyweight.
Subsequent campaigning for the eventual nominee, if that could pay off in unseating Trump, essentially would clinch a Cabinet post, perhaps like his father of Housing and Urban Development.
Yet perhaps he could play his most valuable role in balancing the ticket. Nobody not to the far left can lead national Democrats these days, whether on a presidential ticket or in Congress, but with such a person as a presidential nominee, a running mate that differs a little provides value.
Landrieu fits the bill as he would be almost the only southerner available (Gov. John Bel Edwards has no chance because of unreliably non-liberal preferences he has expressed on some issues such as abortion and the right to bear arms) and provides some minor counterpoints, such as emulating his sister, former Sen. Mary Landrieu, with her view that public policy should make abortion rare but legal for people who choose it, even as she personally would not participate in one. He wouldn’t be the first to make a presidential run hoping for the vice presidential slot.
Louisiana had former Gov. Buddy Roemer take a quixotic shot in 2012 for a minor party, and former Gov. Bobby Jindal while seeking the GOP nomination in 2016 got swamped by the outsider Trump. Unless something big in his life intervenes, the state should get ready for Mitch Landrieu, 2020.