Granted, it’s been a tough two-and-a-half years. The Olympics boondoggle. The routine denial of Freedom of Information requests . The indictments of two top aides for corruption. The epic snow-removal failures of winter 2015. The sacking of Boston Public Library head Amy Ryan — and the subsequent refusal of a new pick to take the job. The crash and burn of IndyCar Grand Prix . Tone deaf responses on everything from residency requirements to the conviction of former Probation Commissioner John O’Brien. The imbroglio at Boston Latin.

Absent a game-changing indictment from United States Attorney Carmen Ortiz — and the controversial prosecutor certainly seems bent on trying -- Walsh is safe. The Boston politics of old is not the Boston politics of today.

So far, it hasn’t been a great first term for Boston Mayor Marty Walsh. Indeed, by some lights it’s been a disaster, and with every screw-up, misstep, cover-up and boneheaded move, one has to wonder: Will he end up being just a one-term mayor?

All of these, in theory, should make grist for any challenger’s campaign mill. Yet so far no one has thrown his or her hat in the ring — and it’s a reasonable bet that no one will. But how can that be?

It’s not as if people don’t want to be mayor. It’s considered a political plum. The late Boston Mayor Tom Menino once described it to me as “the best job in politics,” with vast authority over the day-to-day workings of the city and little check from a structurally weak city council. Thus when Menino announced in March 2013 that he would not run for a sixth term, a large field coalesced, with 10 serious candidates running all-out campaigns to replace him.

Today? Nary a peep from those folks. Much of that is understandable. Some have gone into the administration itself. They, of course, won’t run against the man who is now their boss. Others have gone on with their lives to new careers. But the paucity of candidates speaks not to new jobs and new careers, but rather to the golden god that rules all of politics: money.

Money matters in elections. Big money doesn’t guarantee a win, but it almost always means one is taken seriously. And how does one raise that money? Unless you’re wealthy, the only way is to persuade others to donate it.

Walsh has been an effective persuader. At this point, according to the most recent reports available from the state’s Office of Campaign and Political Finance, he has a balance of more than $1.5 million. That figure itself is intimidating. But when one inspects the source of Walsh’s donations, it becomes clear why no challenger has a chance. Those who give money to the mayor are those with a stake in what the mayor does. Thus, the most frequent contributors are developers, lawyers, union members, business people and (surprise, surprise) city of Boston employees.

So imagine you’re a prospective candidate, trying to suss out a possible run. Perhaps you talk to a few business people and they tell you, off the record, of course, that they think the administration is more than a little bit off its game. So you ask the obvious question: Would you write me a check?

No way.

Campaign contributions are public records. Not only can reporters see them, but so too can the mayor and his campaign staff. The only ones who might give money to an opponent’s campaign are those who never want to work in Boston again.