The apparent success of terrorists in scaring the Spanish electorate into replacing one of President Bush’s closest allies with a strident Bush critic is not merely a disaster for Bush. It is a disaster for the United States, and for whoever wins the presidency in November. Terrorists may seek to use similar massacres to swing our own elections, although that might be more likely to elect Bush than John Kerry. And the rising tide of European appeasement of Al Qaeda and its ilk will threaten to isolate America for years to come.

How should our leaders come to grips with these dangers? One worthwhile step would be for Bush and Kerry to issue a joint statement of national unity, affirming America’s determination to destroy Al Qaeda and its jihadist allies and to fight appeasement no matter who is president. Jim Hoagland recently suggested in his Washington Post column that the two major party chairmen should make a national-unity declaration. But a joint Bush-Kerry statement would be far more powerful.

Perhaps Hoagland thought it a pipe dream to hope for anything that grand from two candidates bent on depicting one another as lying peddlers of pernicious policies. If so, I disagree.

Kerry could use the Spanish tragedy to trash Bush, as Howard Dean has done. Or Bush could use it to trash Kerry. But it would be both smarter politically and better for the country for one of the candidates — either one — to send his opponent a reasonably worded, initially confidential proposal articulating fundamental principles on which they and the vast majority of other Americans agree. (Indeed, Kerry has already said, on March 17: "When it comes to protecting the security of our nation and winning the war on terror, America is unified.")

Such an initiative would put the other candidate in a political box from which he could escape only by making a reasonable counterproposal. Thus would begin a negotiation process in which each candidate would feel political pressure to move toward agreement lest he be blamed for putting politics ahead of national unity.

Dear Senator Kerry (or Dear President Bush):

I am reaching out to you in the hope of transcending our differences and of confronting the dangers dramatized by recent events in Spain, by issuing a joint national-unity statement of principles that we share.

As we both know, the terrorist bombings in Madrid are widely perceived to have been a successful plot to deliver the election to opponents of Bush administration policies in Iraq, Afghanistan, and elsewhere. That perception poses grave dangers for our country regardless of which of us prevails in November, and regardless of whether the Spanish election results are seen as evidence that the administration’s policies have backfired or that the administration’s critics have unintentionally invited further carnage.

These clashing interpretations must not blind us to two grave dangers facing our country. The first is that terrorists will launch further attacks aimed at our own elections and those of other democratic nations. The second is that Europeans and others will seek an illusory protection by appeasing the terrorists and isolating America.

Here is my proposal for a joint statement:

Recent events have convinced us both of the need to come together to emphasize that the American people are united on certain fundamental principles. We disagree vigorously about many issues, of course. They include the wisdom of the current president’s decision to remove Saddam Hussein by military force in the spring of 2003 rather than seeking broader international support. We may also disagree in the future about how best to balance the need for international support and the need for timely action. But upon the following principles our unity is unbreakable:

America will fight terrorism with all its power. We will destroy Al Qaeda and its allies no matter who wins our elections. A president’s paramount obligation is to protect the American people. The faithful discharge of that duty calls for diligent efforts to act in concert with other nations and international institutions; to persuade the people of the world that our cause is just and consistent with their own best interests; and to heed their concerns.

But we reserve the right to use military force — even over the opposition of allies — when necessary to protect against especially grave threats posed either by terrorist groups or by nations that harbor them or may supply them with weapons of mass destruction. Any efforts by terrorists to affect our elections will only redouble our resolve. We will never appease terrorists.

We emphatically reject the stunningly misguided view that the Madrid attacks show that "using force is not the answer to resolving the conflict with terrorists," as European Commission President Romano Prodi recently said. Al Qaeda and its ilk seek to destroy all of Western civilization. Appeasement invites more massacres. And appeasers will forfeit the goodwill of the United States.

I urge you to join me in this statement or, if you prefer, to propose alternative language. I suggest that we make a joint announcement on April 2 at 2 p.m. or any other mutually agreeable time, by coming together at the World Trade Center site or any other mutually agreeable place. One of us could read the first two paragraphs, and the other could read the second two. Take your pick. I offer you this option, and have taken pains to use politically neutral wording, because I care more about reaching agreement on a national-unity statement than about any political consequences.

I pledge to keep this letter, your response, and any related correspondence in strict confidence until at least April 1, to allow time for negotiations over language or other details. If we cannot reach agreement by midnight that day, I will release our correspondence on April 2 at 8 a.m., and let the people judge which of us is to blame for putting politics ahead of national unity. I am assuming the risk that you may see some political advantage in disclosing this initiative before I do. But I implore you to work with me in confidence to reach agreement on a national-unity statement.

The American people will give us both credit if we do so. They will judge you harshly if you reject my proposal without making a reasonable counterproposal. They will judge me harshly if I reject any counterproposal without negotiating in good faith to reach consensus. The good of our country is at stake.

Yours Sincerely,

George W. Bush (or John Kerry)

Suppose Bush sent a proposal like this to Kerry. The senator would suspect Bush of seeking political credit for putting national unity ahead of politics. And Kerry would be right. But he would also be trapped. For all Kerry’s bashing of Bush-style "unilateralism" and "pre-emptive war," and his claims that foreign leaders want Bush out, Kerry’s own publicly articulated policies differ more in degree than in kind. Kerry demonstrated this by voting for war in Iraq and by later rejecting Howard Dean’s position that (in Kerry’s words) the U.S. should "permit a [U.N.] veto over when America can and cannot act … to defend America." The above proposal contains nothing that Kerry could dispute without looking weak on national security. And a flat rebuff to such a Bush overture would make Kerry look unconcerned about the need for national unity in wartime. So the best move politically would be for Kerry to make a counterproposal tweaking the detailed language but accepting the proposal’s fundamental principles.

Now suppose that Kerry sent such a proposal to Bush. The president would also suspect a (partly) political motive, and would also be right, and would also be trapped, by a somewhat symmetrical dynamic: Notwithstanding Bush’s interest in painting Kerry as weak and a captive of the "axis of weasels," the above proposal contains nothing that Bush could dispute without looking unduly contemptuous of world opinion. Again, the best move politically would be to negotiate toward agreement.

Of course, any counterproposal, or counter-counterproposal, could be loaded with language designed to be politically unacceptable to the other candidate. But that would be sufficiently transparent, once the correspondence was made public, to backfire politically.

Would a national-unity statement as vaguely worded as the one above be worth making? I think so, even though it might not stop any bombs from going off in the immediate future. The dynamics of the presidential campaign are fostering the dangerous perception both at home and abroad that America is more divided, Kerry more "multilateralist," and Bush more "unilateralist" than is in fact the case. A national-unity statement would demonstrate America’s underlying bipartisanship in its determination to smash our terrorist enemies and fight appeasement. That might do us some good. Surely it would do no harm.