Much reporting and commentary casts the Senate debate over ratification of the New START nuclear-weapons treaty as driven by partisanship. But New START skeptics are driven by something else: the idea that arms-control treaties should serve our security interests now and in the longer term. New START does neither.

That is why the Senate should consider the full record of the negotiations before voting to approve a treaty that will: 1. encumber our freedom to deploy ballistic-missile defenses, 2. squander the negotiating leverage needed to bring Russian shorter-range missiles under control, and 3. reduce verification standards in this and probably future such agreements.

The first principle of arms control is to negotiate from a position of strength. Our past successes in this field reflected that. Exhibit A: the 1986 Reykjavík summit. Ronald Reagan walked away from an arms-control deal with Mikhail Gorbachev in the face of Soviet demands that the United States encumber the Strategic Defense Initiative (SDI) program. Later, the Russians walked when Reagan proposed completely eliminating intermediate-range missiles in both countries. But the president stood firm until the Soviets returned to the table. The result was the 1987 Intermediate-Range Nuclear Forces (INF) Treaty.

Ronald Reagan knew that in arms control, the United States should play to win. To do that, it had to be prepared to reject an inadequate deal until a useful one could be achieved. The contrast between his negotiating approach and the current administration’s approach to New START could not be more striking.

Ratified in the spring of 1988, the INF Treaty was a watershed: the first accord to actually reduce nuclear arms. It eliminated all nuclear-armed ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 kilometers, together with their infrastructure.

INF negotiations dealt with the most important issue in the U.S.-Soviet strategic relationship from the late 1970s into the mid-1980s: Soviet deployment of SS20 missiles aimed at NATO forces in Europe. These Soviet deployments led NATO to prepare to deploy Pershing and ground-launched cruise missiles. The resulting treaty zeroed out this threat, entirely eliminating a whole class of nuclear missiles.

Prior to the agreement, arms-control enthusiasts accused an author of this article (Perle) of disingenuousness in proposing the “zero option.” The Soviets would never accept it, they argued, so the proposal must be intended to scuttle any possibility of an agreement. But Reagan knew how to negotiate. And he proved virtually the whole arms-control community wrong.

Unlike the INF Treaty, New START would limit a single class of nuclear forces that the Russians are eager to limit. Meanwhile, it leaves another class — tactical nuclear weapons — completely uncontrolled. And in that class, the Russians possess an immense and destabilizing advantage. It is easy to understand why Vladimir Putin is for it. But why would the American president agree?

With the Cold War over, all the conflict scenarios involving the threat or use of nuclear weapons — especially scenarios involving Russia — start (and probably stop) with tactical nuclear weapons. The new strategic situation makes these arms vastly more important than they were when earlier treaties were negotiated. Russia’s tactical nuclear stockpile is publicly estimated to be ten times the size of the equivalent American arsenal, despite our vastly larger global responsibilities. But this is not the main problem with New START.

We live in a post–Cold War world. The United States must balance a rising China along with Russia, while facing potential ballistic-missile threats from Iran and North Korea and other future nuclear states. Yet New START is a throwback to the Cold War paradigm, a bilateral treaty in a multilateral world. Worse, it appears to accept the Russian contention that attempts by the United States to protect itself and its allies with missile defenses are destabilizing.

Reagan’s negotiators went for and got a very good, intrusive, on-site inspection regime for verification. The INF treaty contains the most comprehensive verification regime ever achieved to that point, and the first-ever on-site inspection provisions. Again, most of the so-called arms controllers contended that the Soviets would never accept this. They were wrong.

By contrast, New START has a weak verification regime. Compared with the original Strategic Arms Reduction Treaty (START), it allows fewer on-site inspections. Worse, it restricts inspections to only declared sites — a terrible precedent that could be invoked by states that want to hide their nuclear programs, such as Iran.

Reagan was right to stand firm until he got the INF agreement he sought. That principle also produced arrangements for the eventual conclusion of START and the Conventional Forces in Europe treaties. Reagan never would have shackled our missile-defense program for a treaty that doesn’t add to our security. Yet from its preamble and through its body, protocols, and annexes, New START threatens our freedom to deploy ballistic-missile defenses, limitations that would be in force for the next 10 years, leaving the United States increasingly vulnerable in a dangerous world.

The larger point is that the Russians need this treaty, while we do not. Unfortunately, the administration squandered the leverage this gave us — leverage that could have been used to obtain limits on Russian tactical nuclear forces and avoid any burden on our ballistic-missile defenses. Instead, the Senate now ponders a lopsided treaty that favors Russia and continues the Cold War idea that the dominating balance in the world is between the United States and Russia. This anachronistic notion delights the Russians, but there is no reason why we and our allies should share their enthusiasm.

The INF Treaty was clearly in the U.S. national interest. New START marks a step backwards. Senators would do well to examine the legacy of Ronald Reagan and recall the principle that brought him success in nuclear negotiations. There is a right way to do arms control — and then there is New START.

Dr. Holmes is vice president of foreign and defense policy studies at the Heritage Foundation. Mr. Perle, an assistant secretary of defense in the Reagan administration, is a resident fellow at the American Enterprise Institute.