As Howard Dean rolls toward the Democratic nomination, there seems to be no stopping him. Dick Gephardt is making a last-ditch stand in Iowa as is John Kerry in New Hampshire, but I don't give much for their chances.

Once Dean hits the first multistate primary and faces Wesley Clark for the first time, he will have so much momentum that he will run over the general without even a pause.

In a Bush-Dean race, the contest would likely hinge on three semantic differences. The way the electorate defines the gay marriage, tax-cut and Iraq issues will spell victory or defeat for the candidates.

Dean signed the nation's first civil-union bill, entitling gays to share in the benefits of marriage without using that particular, loaded word. According to the bill, gay couples can inherit from one another as spouses do, can be treated as married for insurance purposes and in health care have the same rights as married couples. Public-opinion polls show that Americans split about evenly on civil unions. But when the words "gay marriage" are presented, they break 3-to-1 against it.

Dean will insist that he does not support gay marriage but only the limited concept of civil unions. Bush will say that if it looks like a duck, acts like a duck and walks like a duck, it's a duck. Bush will characterize the Dean bill as a gay marriage act and will challenge Dean to approve of the Defense of Marriage Bill that prohibits homosexual marriage.

The former Vermont governor has also proposed repealing most if not all of Bush's tax cuts. Again, polls indicate that Americans break about 50-50 on this issue. But Bush will say that Dean wants to raise taxes - a 2-to-1 no-no in public-opinion polls.

Is the glass half empty or half full? Is a repeal of a tax cut that has been on the books for several years tantamount to a tax increase? This battle, too, will absorb Americans for much of the general election campaign.

Then there is Iraq. It is very well and good to seek the Democratic nomination by offering a history lesson opposing the invasion of Iraq.

But by next November, Dean will have to offer more. He must address the question of whether we should retreat under fire, leaving Iraq to the tender mercies of the terrorists or whether we should persevere, refuse to run and gradually empower and enable an Iraqi government and accompanying military presence.

The Vietnam War opposition was animated by pleas for bombing pauses, negotiation and a variety of other reasonable alternatives to evacuation. The Iraqi War peace movement has yet to articulate these halfway postures and risks being painted as capitulationist.

So how can Bush transform the debate over civil unions to a referendum on gay marriage; morph the proposal for repeal of his tax cut into a bid for new taxes, and fast-forward the debate over Iraq to one of retreat vs. staying the course?

Early media is the answer. As soon as the Democratic candidate is chosen, before he has time to reload his depleted coffers, Bush must strike aggressively and characterize the issues in his own light and cast them to his advantage.

In this task, he may have an unwitting ally in the campaign-finance laws. Most of the Democrats, probably including Dean, will accept federal matching funds, which place sharp limits on their allowable campaign spending in the period before the Democratic National Convention. Bush is not taking these funds and would be subject to no such limitation.

Bush could enjoy a virtual monopoly of advertising time in the crucial period after the Democratic primaries in March and the national convention in August. He could win the election in a spring offensive

Dick Morris is a Fox News contributor and author. His latest book is "Here Come the Black Helicopters: UN Global Governance and the Loss of Freedom." Visit his website: www.dickmorris.com and follow him on Twitter@DickMorrisTweet. Click here to sign up to get all of Dick's videos emailed to you.