Mayor Bloomberg’s plunge into the election season as a booster of independents and moderates is stirring what the New York Times, in its leading story this morning, calls “a new round of speculation about his presidential ambitions.” It caught our eye because these columns were second to none in urging Mr. Bloomberg to get into the presidential race in 2008, and it happens that we feel the same way now.

Back then, our issue, as we wrote a bit self-satirically, was that it would be good for The New York Sun’s circulation were the nominees for president to be Mayor Giuliani of New York for the Republicans, Senator Clinton of New York for the Democrats, and Mr. Bloomberg of New York as an independent. What was it that Engine Charlie Wilson said about how what’s good for GM was good for the country? That’s similar to how we felt about the 2008 race.

Satire aside, it was our view that it actually would have been good for both New York and the country if Mr. Bloomberg had dived into the race in 2008. And it cannot be less so with the even broader divide that is yawning between the two major parties today. The mayor has proven himself to be smart, hale, and prepared to risk his own fortune on a campaign that he thinks he can win. And our political debate needs all the contenders it can get.

It’s not that our admiration for Mr. Bloomberg is unalloyed. On the contrary, no editorial columns — not in New York or elsewhere — have been as caustic in criticizing the mayor as have been the columns in the Sun. We’ve opposed him on his nanny-statism (as in “Bloomberg Fries”); his campaign against guns (“Bloomberg’s Foot”); and on his occasional lapses of moral judgment (“The Bloomberg-Fulani Initiative”), to mark but a few differences. Nor have we spoken in dainty terms. One editorial, “Bloomberg’s Disappointing Side,” began this way:

“Mayor Bloomberg’s statement opposing the confirmation of Judge John Roberts to the Supreme Court generated among many New Yorkers a rush of disgust. It epitomizes everything that many of us see as the disappointing side of the mayor — his spinelessness, his tendency to pander, his disregard for political loyalty, his self-righteousness when it comes to what he defines as matters of ‘public health,’ his special interest-driven politicking accompanied by blather about how he isn’t motivated by politics. His allegiance only to himself. His abuse of public resources. His arrogance. His hypocrisy. His combination of grandiosity and smallness. Not since Senator Kerry have we seen a politician who can be as oleaginous as Mr. Bloomberg.”

Let the record also show, however, that a few days before that harangue, we had endorsed Mr. Bloomberg for a second term, because he was better than the Democrat. He has run a relatively calm administration and been sagacious in his hiring and exemplary in his preparedness to delegate. His schools commissioner, Joel Klein, has been a leader of the charter school experiment, and his commissioner of police, Raymond Kelly, is almost without peer in public life.

The mayor himself has emerged as a leading voice in favor of immigration into this country, which by our lights is reason enough for him to get into the race. If the Constitution places responsibility for immigration in the federal government, Mr. Bloomberg, given his pro-immigration record, would be an ideal man to take on gaining control of our borders. Wouldn’t Mr. Kelly, who was once United States Customs Commissioner, be a magnificent choice to lead an effort to gain control of our borders in a way we could all — from the Rio Grande to Brighton Beach — be proud of.

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Mr. Bloomberg may not have as profound a comprehension of the political economy or the Constitution as, say, Governor Palin, whose praises we have been singing in these columns since Senator McCain ushered her onto the national stage. But it’s not Mrs. Palin and the partisans of her soaring theme of constitutional conservatism who would have to worry about him. The camp Mr. Bloomberg would draw from is of those who voted for President Obama and woke up to discover that the change they’d gotten locked into was the far-left agenda of the public-service- and teachers- unions, the tort bar, with a strain of anti-Wall Street demagoguery, class warfare and even, we predict, protectionism. The mayor has a rarely matched comprehension of the global nature of our economy (he employs, in his news service, more foreign correspondents than any American in history). He, like a number of others in the political lineup, has his own deeply American and inspiring personal story. And it’s hard to think of a reason for him not to enter the fray.