If President Bush wins the election, his victory will come in part because his party has a strong domestic agenda. If Senator Kerry loses, it will be because of his party’s lack of one.

That is one of the conclusions we can draw as the convention season ends. Consider what has happened in New York and in Boston before it.

New York: Some of the presentations at Madison Square Garden were downright painful. The Bush daughters did the entire female sex a disservice with their “young women can be goofs” performance. Other speeches were weak. Then there were those autobiographical details. The Depression-era parents and grandparents so praised by the speakers would have been put off by their descendants’ sentimentality.

Still, the Republicans’ rehearsal of the American success story reflected a consistent policy message. We are micro-economists, they were saying; we focus on property ownership and shareholding and our model is Ronald Reagan. “Faith in the free market,” rumbled Governor Schwarzenegger. “The key to a richer culture is a strong family,” intoned Rick Santorum, the Pennsylvania senator.

Democrats accuse Republicans of using conventions to hide their radical agendas. Madison Square Garden belied that accusation. After all, Mr. Schwarzenegger did not gently peddle compassionate conservatism. He commanded: “Don’t be economic girlie-men.”

Boston: The Democratic Convention by contrast offered – what? The rebuttal to reliance on the private sector is to stress the importance of the public sector. The reply to the argument for individual ownership and control is the argument for the good of the collective. But Democrats instead nervously advocated the free market. At times they were indistinguishable from Republicans. “We believe the private sector, not government, is the engine of economic growth and job creation” – the phrase comes not from Mr. Schwarzenegger but from the Democrats’ 2004 platform. “We can strengthen and lift up your families” – the line is from Senator Edwards, the vice-presidential candidate, in Boston, not Mr. Santorum in New York.

In Boston, party leaders also stressed middleclass pain and argued for restoring government benefits even as they championed deficit reduction. The policy conclusion: Republican inconsistencies exist but Democrats’ inconsistencies are greater.

Political observers blame Mr. Kerry. The Democrats, so goes the thesis, need not “Senator Flip-Flop” but a candidate like Bill Clinton. The reason Mr. Kerry flails is that he is no Clinton.

The Clinton comparison, however, is not fair. For while Mr. Kerry may be opportunistic, his policy trap was laid by Mr. Clinton himself – and by Dick Morris, Mr. Clinton’s cheery, fickle political adviser. The pair, along with then-young groups such as the Democratic Leadership Council, established a different model of Democrat, the New Democrat.

To the chagrin of traditional Democrats, New Democrats treated the old ideas of Lyndon Johnson as something vaguely shameful. The Democrats’ job was to capture the center, even the center-right. Or, in other words, steal the opponent’s ideas, then marginalize him as an ideologue.

This tactic can work, especially in good times and especially with a likeable candidate such as Mr. Clinton or Prime Minister Blair. Mr. Kerry clearly thinks so. He signed the Hyde Park Declaration, a manifesto of New Democrats created at Franklin Roosevelt’s home on the Hudson River.

But while “triangulating,” as it is known, may be good for the individual candidate, it is not good for the party in the longer run unless both leadership and base are committed to a philosophical change. And many Democrats – indeed many Americans – still believe that rights are about entitlement, not the chance to compete. The result is that the party comes off as cynical and loses support.

Democrats are resorting therefore to bashing their opponent, both on policy grounds and personally. Bashing, after all, is easy and pleasurable – in no small part because it generates such a reliable echo from abroad. When North Korea’s leader recently characterized Mr. Bush’s job performance as “imbecilic,” one could not help wondering whether he had been in touch with the Democratic National Committee.

Given the enormous uncertainty over the Middle East, bashing Mr. Bush may indeed be enough to win Mr. Kerry the presidency. Still, without policy to reinforce it, bashing can backfire. Consider the Republicans, whose ideas Mr. Clinton kidnapped in the 1990s. They threw policy discussions out of the window and, for years, devoted themselves to president-bashing of an intensity not seen again until the premiere of Michael Moore’s “Fahrenheit 9/11.”

Note to Democrats: as 1996 demonstrated, this behavior can lose a party a presidential election.