The weaknesses of President Obama’s New START treaty with Russia are finally starting to surface in Washington. On Monday, Mitt Romney weighed in against the treaty in a Washington Post column. The former Massachusetts governor raised concerns previously aired by Amb. John Bolton (in National Review), by the Heritage Foundation’s Dr. Kim Holmes, and — in testimony before the Senate Foreign Relations Committee — by former undersecretaries of state and defense Bob Joseph and Eric Edelman.

Yesterday, Sen. John Kerry (D-Mass.), reacted with a column that, after attacking Romney personally, merely ignored or dismissed (rather than disproved) Romney’s objections.

First and foremost, Romney objected to START on the grounds that it would impede America's ability to complete a global ballistic-missile-defense system. The evidence supporting this concern is overwhelming. Article Five of the treaty explicitly prohibits the conversion of former ICBM silos to the purpose of missiledefense; the Russians have publicly stated that the treaty limits America’s discretion to complete ballistic-missile defense, and the preamble of the treaty explicitly links reductions in offensive capability to reductions in defensive systems.

Those who think the preamble unimportant should consider the words of Russian general Yevgeniy Buzinsky, chief of the International Treaty Directorate in the RussianDefense Ministry: “This [treaty language on missile defense in the preamble] makes it possible for us, in case the Americans increase their strategic ABM system, to claim that they are not observing the [terms] of the treaty.”

Senator Kerry’s response not only fails to answer these concerns, it actually lends credibility to them. Kerry states that the preamble to the treaty is not binding by itself and denies that the treaty “impedes our ability to build missile defense against attacks from rogue countries.” He does not say that START would leave America free to construct a missile-defense system that could be used against Russian nuclear missiles.

And that’s the crux of the matter. There is powerful evidence — especially in the context of the president’s decision last year, at Russia’s insistence, to abandon the Polish and Czech missile-defense bases — that the treaty reflects an agreement that the United States will not build a missile-defense system that could be used against Russia. The implications of that agreement go far beyond America’s relationship with Russia, because it is impossible to build a robust missiledefense against, for example, Iran, which could not also be used against Russian missiles. So to the extent that START limits missile defense against Russia, it must and will narrow the options we have to defend against Iran, and, for that matter, North Korea.

That is a key point that Romney and others are making. The Senate simply must demand a satisfactory answer. Ballistic-missile defense may be the most important defensive system the U.S. is building today. Even if the New START agreement were otherwise better than it is, the benefits would not come close to justifying any sacrifice in America’s ability to defend itself against nuclear missiles.

Romney and other critics make several other points that Senator Kerry leaves effectively unrefuted:

1. Romney points out that START gives too much power to a “Bilateral Consultative Commission.” It would be able to make unilateral changes in the treaty with regard to missile defense. Senator Kerry claims that the treaty requires any such change to be ratified by the Senate. Actually the treaty permits the commission to agree unilaterally on changes that are not substantive, but never defines what is or isn’t substantive. Such ambiguity gives critics a right to be concerned. It would help if the White House would release the negotiating record of the treaty to clarify the meaning of provisions like this; but so far it has refused to do so.

2. Romney claims that the treaty favors the Russians in three important areas: It does not limit tactical nuclear weapons, which permits the Russians to retain their huge advantage in that area; its limits on launchers will require the U.S. to reduce its capabilities while letting the Russians increase theirs; and it permits the parties to put ICBMs on bombers and rail-based launchers. Kerry doesn’t address the first two points, implicitly conceding them. On the last point, he ignores the issue with rail-based ICBMs (even though the Russians had rail-based ICBMs during the Cold War) and claims that if the Russians were “foolish” enough to put ICBMs on bombers, the U.S. could “get the new weapons incorporated in the treaty or withdraw” from the treaty. This argument concedes that, as critics claim, the treaty currently does not cover using bombers for ICBMs.

So far, supporters of START have acted as if the treaty were a kind of aspirational expression of the desire for a nuclear-free world, and that anyone who opposes it is an enemy of such a future. But no one should doubt that this START treaty, like its predecessors, will require real changes that will have a real impact on American security. The more the administration ignores or dismisses the concerns of critics, the clearer it is that the changes embodied in this treaty will not be for the better, and could be disastrous. As the case now stands, the Senate should vote against ratification.

Jim Talent, a former member of both the House and Senate Armed Services Committees, is now a Distinguished Fellow at the Heritage Foundation.