American soldiers during Afghan National Army training at Camp Bastion in Helmand Province, Afghanistan,

American soldiers during Afghan National Army training at Camp Bastion in Helmand Province, Afghanistan, in March. This year’s presidential campaign has hardly touched the war in Afghanistan.

The United States will soon mark 15 full years of war in Afghanistan, but you wouldn’t know it from the political discourse.

Democrats and Republicans seem to have something of a rare, if unspoken, truce on the subject. Even amid deepening partisan polarization, with the most frivolous issues seized for political gain, no one seems eager to discuss a war that is still costing American lives and hundreds of billions of dollars.

This year’s presidential campaign, in which mass deportations and the NATO alliance are on the table, has hardly touched it. When Hillary Clinton and Donald J. Trump squared off at a recenton national security issues, they were surrounded by an audience of veterans, many of whom had fought in Afghanistan, but the war And though the election has grown most heated over terrorism and immigration, the candidates showed rare restraint on Monday, when the police arrested an Afghan-born American citizen, Ahmad Khan Rahami, on suspicion of planting bombs in Manhattan and New Jersey.

Mr. Trump’s response was typically harsh and Mrs. Clinton’s typically detailed, but neither had much to say about Afghanistan. That is a conspicuous and newfound prudence for both candidates, who have been eager to discuss Syria and Iraq immediately after terrorist attacks linked to those countries.

Whether or not investigators find connections between these bombings and American action in Afghanistan, it is increasingly apparent that America’s public and policy makers alike would rather not address their faraway, largely failed war.

Neither party has an incentive to call attention to this bipartisan failure. Neither has a better policy to offer. And neither sees any political gain in raising it. Voters, entering their fourth consecutive presidential election with the United States at war, seem happy to pretend that the Afghan war, which has killed more than 2,300 American service members, doesn’t exist.