Installing jogger-friendly, low-maintenance rubber sidewalks (a pet of City Councilor Rob Consalvo) and coordinating new business development with Cambridge (Councilor Mike Ross) are just two of the dozens of innovative ideas that emerged from the four-month, 12-candidate, nonpartisan Boston mayoral primary.

As smart and as engaging as those ideas are, they were, in part, attempts by the candidates to reshape the political terrain. That is what idea-driven campaigns are all about, persuading voters to support a politician who advances a thoughtful agenda.

Now, however, that the campaign to succeed Mayor Tom Menino, Boston’s longest serving mayor, has entered its final five weeks, it is important to recognize that there are four overarching issues that will determine the success or failure of the mayoralties of the two final contenders, City Councilor John Connolly of West Roxbury, and State Rep. Marty Walsh of Dorchester.

These four issues cannot be avoided. In and of themselves, they are immensely important, rippling across city government in expected and unexpected ways. They are at the core of the political and policy landscape. They define the reality of the next four years — and beyond.

Pensions and related costs are the driest, least sexy, and perhaps most important item on the agenda. Voters are not going to hear snappy talking points or watch riveting commercials about maintaining the fiscal discipline needed to keep Boston from becoming the next Detroit. The Motor City slid into bankruptcy earlier this year in large part because of its inability to calibrate its outflow with its income. Detroit’s pension and retiree health-care costs sit at $9.2 billion, or more than half of its total $18 billion debt.

Detroit, of course, is a worst-case scenario, the nation’s poster child for corrupt and irresponsible governance coupled with historic industrial decline.

On the other hand, if there were an Ivy League of municipal finance, Menino’s Boston would be in it.

It is a gross oversimplification, but a case could be made that successful 21st century cities will be those that have vibrant local economies as well as administrations that have come to terms with the potential punishing pension obligations wracked up over the last 40 or so years.

Boston’s relative prosperity — and if you are a blue-collar, undereducated, or minority worker, it is very relative — rests on the city’s vibrant financial-services, health-care, and university sectors.

Thanks to Menino’s old-fashioned sense of fiscal prudence, Boston is on track to have zero unfunded pension liabilities by 2025. That’s just 12 years from now. Over the last 20 years, Menino has mopped up the largely unrecognized fiscal mess left by his predecessor, Ray Flynn, while simultaneously keeping Boston in the good graces of the Wall Street sharks who — like it or not — play a quiet but outsized role in governance.

As admirable as Menino’s performance has been, there is still important work to be done. The next mayor is not only going to have to continue to match Menino’s overall financial skill, he is also going to have take the steps to get a firmer handle on what bean counters call “other post-employment benefits” (OPEB). Translation: health care and life insurance for retirees and their families.

OPEBs exceed $3 billion. These unfunded benefits are almost triple the cost of the pensions themselves. The city is successfully using acceptable stopgap measures to keep these unfunded liabilities under control. Nevertheless, The Boston Municipal Research Bureau, the city’s nonpartisan watchdog, urges the establishment of a dedicated trust fund, a more formal mechanism for whittling down these billions in debt, as well as a more conservative calculation of the return on the investments that secure retiree’s benefits.

The bottom line? Simple: Campaigns are about promises and promises cost money. Which candidate for mayor has the discipline to keep pensions and other costs under control as well as the imagination to get more bang for the buck from existing tax revenues?

Collective bargaining is the wild card of city governance. When it comes to dealing with Boston’s increasingly militant public employee unions, a mayor can often feel as if he faces a lose/lose situation. Taxpayers are more anxious than ever as a result of a flatlining economy. In addition, for more than 30 years, economic trends have punished the poor and the working and middle classes.

But thousands of city workers are constituents too. They tend to want to maximize pay raises and benefits. And they vote — in greater proportion than average citizens.

Last week’s news that an arbitrator awarded the Boston Patrolman’s Union a contract with salaries and benefits totaling $80 million more than the city wanted to pay induced apoplexy in Menino.

Candidate Walsh asserts that if he were in charge, this would never have happened. Walsh contends that his team at the negotiating table would have brought a better result. With all due respect, that’s easy for Walsh to say. “What ifs” can be dicey propositions at election time. WGBH News contributor David Bernstein, writing in his Boston magazine blog, makes a persuasive case that Walsh is trying to have it both ways, favoring at the State House a mandatory form of arbitration, but decrying the results of binding arbitration when applied to this police contract.

However the police contract is settled, collective bargaining is now clearly an election issue. Once the police contract is history, only about 25 percent of the other union agreements remain to be negotiated. But among those are the contracts for the Fire Department, the only public employee union to endorse Walsh. The Boston Teachers Union endorsed Councilors Felix Arroyo and Consalvo, who failed to make it to the November final.

The teachers union, it should be noted, are frosty toward Walsh, who in the past has been an advocate for charter schools, and openly hostile toward Connolly, the only city councilor to vote against the most recent teachers' agreement.

Education is the issue that compels the most emotional engagement in this campaign. Reformers are still bitterly disappointed that the teachers’ contract failed to secure a longer school day and grant school principals and headmasters greater autonomy.

At the moment, these issues may not be in the headlines, but politically active parents and downtown businesses concerned about the future quality of their workforces are still focused on them. The next mayor will be taking a commanding step when — together with the School Committee — he selects a new school superintendent.

Public safety means different things to different neighborhoods. Crime is down in the Boston as a whole, but in swaths of Dorchester, Roxbury, and Mattapan, and slivers of Jamaica Plain and the South End death and violence by gunplay is tragically and unacceptably high.

City Hall funnels millions of dollars in federal aid into those neighborhoods in an attempt to stem the largely gang-related violence. But the social problems of low incomes, poor education, substance abuse and addiction, and the lack of economic opportunity make it almost impossible to turn things around.

It is difficult for residents in West Roxbury or in other more stable parts of the city to grasp the pervasive and potent unease that afflicts even the most stable and traditional families in the afflicted neighborhoods.

The next mayor will appoint a new police superintendent, but despite the criticism that surrounded outgoing top cop Ed Davis, it is difficult to imagining anyone doing a substantially better job unless more police are sent to the area — and that costs money.

There are, of course, many more issues in this campaign than pensions and city finance, collective bargaining, education, and public safety.

Economic development and jobs, affordable housing for workers of all stripes, the place of artists and the arts, transportation, a vision for public park, diversity, and social justice are all important issues.

But safety, schools, employee relations, and finance cannot be avoided. Other issues, such as transportation, may require mayoral leadership, but success will ultimately be secured through cooperative action at the state and federal level and by working with the private sector.

As for the Big Four, they belong to the next mayor.