The treaty has been endorsed by nearly every luminary in the Democratic and Republican foreign policy establishments — including Henry Kissinger, George Shultz, James Baker, Sam Nunn, William Perry and James Schlesinger — as well as all three heads of the nation’s nuclear laboratories and seven former commanders of the nuclear forces.

That should make Senate ratification certain. But some Republican members — including Jon Kyl, James Inhofe and Jim DeMint — are still balking. Cold war habits and specious arguments die hard.

The critics’ biggest objection is that the treaty will somehow constrain American efforts to build missile defenses. They point to a line in the nonbinding preamble about the “interrelationship” between offensive and defensive strategic arms and a provision in the treaty that bans the use of missile silos or submarine launch tubes to house missile defense interceptors. Never mind that American commanders have no interest in using either that way.

We are no big fans of national missile defense — the technology has yet to show that it can work. But the Obama administration is moving ahead with a limited program. And Defense Secretary Robert Gates has testified that the New Start treaty will impose “no limits on us.”

Critics also charge that the Russians can’t be trusted, pointing to a recent State Department report that acknowledged several unspecified compliance disputes related to the Start I treaty. But it also said Russia lived up to the treaty’s “central limits.”

What the critics don’t mention is that Start I expired last December. If the Senate fails to ratify New Start there will be no inspections and no data exchanged.

Finally, critics claim that the Obama administration isn’t doing enough to “modernize” the weapons it retains. If we have any complaint, it is that President Obama has gone too far to appease the nuclear lab directors and Republican critics on this point. He has promised $80 billion over the next 10 years to sustain and modernize the nuclear weapons complex and $100 billion to refurbish nuclear weapons and delivery systems.

At a time of huge deficits and two costly wars, that is far too much to spend. The United States already has a robust and costly program to ensure the safety and security of its existing nuclear weapons for years to come. President Obama certainly must continue to resist pressure to build an unnecessary new weapon.

The political motivation of the anti-Start crowd is all too clear. One leader is former Gov. Mitt Romney, a once and maybe future presidential candidate who is firing up potential supporters with a charge that the treaty could be Mr. Obama’s “worst foreign policy mistake yet.”

John Kerry, chairman of the Senate Foreign Relations Committee, has set a committee vote for Wednesday. He has made clear that he and Richard Lugar — the ranking member and the Senate’s most respected expert on arms control issues — are still searching for enough Republican backing to get the required two-thirds vote.

Two decades after the fall of the Berlin Wall, the United States and Russia still have more than 20,000 nuclear weapons. That is absurd. The Senate needs to pass New Start now.