Good leaders make things possible. Great leaders, it is said, make them inevitable. Few would claim Mayor John DeStefano Jr. belongs to the rarefied group of the latter. In the last two years alone, the centerpiece for his economic development plan — a $500 million mall — unraveled; plans to forge closer ties with neighboring towns that soak up New Haven’s resources sputtered; and a costly land deal between a politically connected developer and city attorney revealed just how unaccountable City Hall development remains.

And yet. Life in this patchwork city of 123,000 keeps improving — witness the sustained economic growth, reduced crime, improved city services, strong bond ratings and the expansion of downtown housing and commerce. The simple question confronting voters Tuesday is whether to credit the change to historical happenstance or the mayor himself.

The answer, in large part, is DeStefano. As he fights for a fifth term, the mayor presides over a city he has helped transform. Reconstructed schools. New downtown storefronts. Downright connubial relations between Yale and the city. That is why the Yale Daily News today endorses John DeStefano for re-election against state Sen. Martin Looney in tomorrow’s Democratic primary.

In the end — after months of debates, door-to-door campaigning and at times outrageous antics — the case against the mayor was not successfully made while his record of effectiveness became increasingly clear.

Looney, who represents portions of New Haven and surrounding towns at the state level, has focused attention on three major gaps in DeStefano’s agenda and resume: a top-heavy public school administration, unbalanced downtown development and the ethical scarlet letter affixed to mayor’s chest.

But Looney’s key proposal for downtown development — a minor-league baseball stadium — is foolhardy. The project will cost millions, perhaps experience a honeymoon period of success, but promises no long term profitability. His stubborn association with the political detritus of the old Democratic Party in New Haven — the same names DeStefano scuttled over the last four years — undercuts his claim to reform-minded politics. And his relentless use of anti-Yale rhetoric on the campaign trail and in bizarre recent mailings threatens to undermine the city’s most important political and economic partnership.

The Looney campaign’s most glaring failure is its singular inability to prove that the senator can do a better job than the incumbent. “Eight years is a long time to be in power,” Looney told the News’ editorial board, sounding a recurring theme of missed opportunities. But politics is the study of missed opportunities; at times Looney appeared to believe simply pointing them out lent legitimacy to his candidacy.

Why trust DeStefano? It is a reasonable question. Because the the man whose name was once synonymous with scandal has turned his administration inside out, hiring the smart, young and squeaky clean Henry Fernandez to direct the city’s development; making a clean break with the ethically challenged development director Salvatore Brancati Jr. and party boss Nick Balletto; and bringing aboard his campaign progressive partners like Julio Gonzalez ’99. We entrust him once again with the city’s future.