Donald Trump wants NATO members to pay their fair share into the transatlantic alliance, and that idea is nothing new. Since the end of the Cold War, every American administration has made the same demand.

And it’s still a bipartisan stance. Leaders and candidates in both parties — from Bernie Sanders to Senate Foreign Relations Committee Chairman Bob Corker, R-Tenn. — have called for NATO members to put more skin in the mutual defense game.

Some of our allies have done just that. In particular, the leaders of Central European countries who most intensely feel the pressures of Russian adventurism, know they need to shoulder their share of the load. At the 2006 Riga Summit, NATO heads of state agreed that European members of the alliance should spend at least 2 percent of gross domestic product on defense.

Estonia has met that commitment, and others are working in that direction. In fact, in 2015, 19 NATO members halted what had become a pattern of cuts to defense spending, and 16 of those nations actually increased spending.

The 2 percent pledge makes sense. A sustained commitment to maintaining armed forces over time makes for a better, more cost-effective defense. Whipping the size of defense forces up and down like a thermostat is what drives a lot of the inefficiencies for maintaining sufficient ships, planes and troops to reassure allies and deter potential enemies.

GDP works as a general measure of obligation much in the way families set aside a portion of their income for housing, savings and other vital expenses — ensuring that essentials are paid for first and that the family can live within its budget.

The American economy is roughly the same as Europe’s, yet U.S. defense commitments to NATO plus Asia and the Middle East are twice as big. For America, 4 percent is not unreasonable. Half that, 2 percent for Europe, sounds about right as a rough, baseline measure.

And there is a need for NATO to be a capable force. The stronger NATO is, the less tempting it is for Russia to meddle in transatlantic affairs, the better the transatlantic community can respond emergencies arising from an unsettled Middle East, and the better the alliance can deal with emerging threats like cyber warfare and transnational terrorism.

What jarred many in Washington and other capitals was how Republican presidential candidate Trump suggested he would push other NATO nations to fulfill their burden-sharing commitments by making U.S. commitments contingent on theirs.

Certainly there are other ways by which the U.S. could help its NATO allies up their game. Boost the transatlantic economy. This will help us and our allies afford the defense we need. Reaching a U.S.-U.K. free trade agreement would be a huge benefit; the two countries account for about 80 percent of NATO’s capabilities.

Lead by example. Washington should build back to having four U.S. brigades permanently forward-deployed in Europe.

And, with the European Union unraveling, make NATO a strong political alliance.

NATO needs to get better. And America needs a better NATO.

James Jay Carafano, an Army veteran, directs research on foreign policy and defense issues for the Heritage Foundation.