Democratic nominee John Kerry’s harsh new attacks on President Bush’s Iraq policy beg a vital unanswered question: OK, Mr. Kerry, what would you do?

Kerry has been all over the place on the Iraq war — so much so that we can’t be sure whether he would have fought it in the first place (probably not) and whether his future strategy rests on winning the conflict or getting U.S. troops out as quickly as possible.

[IMGCAP(1)] What we do know for sure about Kerry’s Iraq policy is that he would try to enlist other countries to share the burden. But suppose they refuse, as seems likely? Does President Kerry “stay the course,” as Bush says he will, or find a way to withdraw?

Americans are not the only ones who deserve a thorough answer. Last week on the National Public Radio program “To the Point,” Washington Post Baghdad reporter Jackie Spinner said that Iraqi leaders are afraid that Kerry will be elected and pull U.S. troops out, leaving them to face insurgents alone.

With most U.S. polls now showing that Kerry trails Bush by a decisive margin — and officials in both campaigns agreeing that Bush is ahead — Kerry’s attacks on Iraq seem to represent a shift in strategy.

During the Democratic convention, aides to Kerry said they were satisfied that most voters had decided they didn’t want Bush to continue in office, so their job was simply to make Kerry appear to be an acceptable alternative.

Even during the GOP convention, Kerry aides said that Kerry would concentrate this fall on positive messages about the economy and health care.

His ads in battleground states do emphasize the economy, though they also exhibit a strong anti-Bush edge. Still, the dominant theme of his stump speeches last week was that Bush’s policies in Iraq have been “catastrophic.”

Evidently, Kerry strategists — reinforced by new recruits from previous Bill Clinton campaigns — have decided that voters haven’t rejected Bush after all and that they need to be reminded of his failings.

So Kerry tells audiences that, because Bush “went it alone, we are bearing the burden and paying almost any price alone. Almost all the casualties are the sons and daughters of America. And 90 percent of the costs are being met by Americans — the total so far, $200 billion and rising every day …

“That’s $200 billion we’re not investing in homeland security to keep cops on the street, to protect our airports, our subways. … Wrong choices, wrong direction, wrong leadership for America.” Sometimes, he says the money could be spent on health care or after-school programs.

But that raises the question: How much would Kerry spend on Iraq? And, more importantly, what would he do to correct “the mess” he says the Bush policy has produced?

In his recent speeches, Kerry has been saying, “It’s not that I would have done one thing differently in Iraq. I would have done almost everything differently. It was wrong to rush to war without a plan to win the peace. It was wrong not to build a strong international coalition of our allies.”

According to The New York Times, the Kerry campaign passed out a memo to reporters that said, “The reason Iraq is an issue in this campaign is NOT over the question of whether it was right to hold Saddam Hussein accountable. The reason is because of the way George Bush went to war, making the wrong choices and weakening the United States at home and overseas.”

I think one of the reasons polls show that Bush leads Kerry on issues of leadership and on who’s best to handle Iraq — 53 percent to 37 percent in the latest Washington Post/ABC poll — is Kerry has left it unclear whether he would have fought the war at all.

He has horribly confused everyone — and suffered for it — by saying last month that, even knowing that Hussein lacked weapons of mass destruction, he still would have voted to authorize Bush to go to war in October 2002.

Yet, he’s also borrowed the line from former rival Howard Dean, an opponent of the 2002 resolution, that it was “the wrong war, in the wrong place at the wrong time.”

Personally, I can’t believe Kerry would have voted for the resolution if he had known WMD didn’t exist. He voted against the 1991 Gulf War, after all, when Hussein had unmistakably invaded Kuwait. His credibility suffers when he says he would have voted with Bush.

But almost certainly, he would not actually have gone to war, preferring to allow U.N. weapons inspectors to wander around Iraq for months. When they found nothing, he would have pulled U.S. troops out of the region — if he’d put them there at all.

And after that, he would have had a hard time resisting French, Russian and German pressure to lift economic sanctions against Iraq and remove inspectors. And then, if Hussein wished, he could have resumed his WMD programs unimpeded by anyone.

And then, if he wished, Hussein could have passed the weapons along to terrorist groups. This, fundamentally, was the scenario outlined by Sen. John McCain (R-Ariz.) in his speech to the GOP convention — a more effective linking of Iraq to terror than even Bush has put forward.

But whatever might have happened in the past, what’s important is what each candidate would do in the future.

Even though Bush — mistakenly, I think — has resisted raising U.S. troop levels, it’s clear that his emphasis is on seeing through a successful transfer of power to Iraqis and suppression of resistance by insurgents.

Kerry has said on some occasions that he would abide by the judgments of U.S. military commanders on troop levels.

But his emphasis has more often been on withdrawal. In May, he said he would withdraw troops “sooner than Bush would.” On Aug. 8, he said he would “significantly” reduce the number of troops “within six months” of taking office. On Aug. 9, he said he hoped to begin withdrawals “within a year.”

Lately, he’s said, “My goal would be to try to get them home in my first term” and to begin withdrawing “as soon as possible.”

What’s missing from Kerry’s speeches is any declaration that “we’ve got to win this war” or “we’ll stay ‘til we prevail.” Americans may be dubious about whether the Iraq war was “worth it” — but they certainly don’t want to lose it. That’s why they trust Bush more than Kerry.