A careful look at the dynamics of the 2008 election, and of the current policy environment, suggests that the case for Gore to join the race is quite powerful, both from his own perspective and that of the Democratic Party.

From his vantage point, there are two main considerations. Gore, 59, needs to assess whether he can win and whether his policy differences with the other candidates are serious enough for that win to matter. Both considerations should push him heavily toward running.

The national polls certainly are discouraging for him. A recent Gallup/USA Today poll that included Gore in a Democratic field gave him only 10 percent of the vote, putting him in a tie for third place with former Senator John Edwards, a whopping 33 percentage points behind Senator Clinton, who's also 59.

Still, it's hard to know whether such a poll has any meaning given that Gore isn't actually in the race. Voters, after all, wouldn't want a president who doesn't want the job.

Polls also indicate that Clinton is much more vulnerable than the national figures suggest. First, she is struggling in Iowa, and a loss in Iowa, as Howard Dean can attest, can upend a campaign. Her weakness reflects an underappreciated fact: The famed Clinton political machine doesn't extend into the Hawkeye State. Indeed, back in 1992, Bill Clinton blew off Iowa completely.

Gore Can Take Iowa

Hillary is only up by 3 percentage points, on average, in Iowa polls over a surprisingly weak Barack Obama. One poll conducted by Newsweek even has Obama ahead in Iowa by 4 points.

While Obama is probably not a strong enough candidate to embarrass Clinton in Iowa, Gore could easily do that. In contrast to Bill Clinton, he was enormously popular in Iowa, winning 63 percent of the vote in 2000, at a time when Bill Bradley was still considered a serious candidate.

Gore also has the broadest grassroots support of any unannounced presidential candidate in recent memory and could build an impressive ground game in a short time.

DraftGore.com, an organization that has arisen with the sole purpose of encouraging his candidacy, already has 179,000 signatures on a petition for him to run. One would guess that a win in Iowa would just about K.O. Clinton's hopes for a runaway nomination.

Strong Policy Case

On whether it matters for policy reasons, the case for Gore to run is much stronger. He has made global warming his defining issue, and the dirty secret of the Democratic race is that Christopher Dodd, as the lone supporter of a carbon tax, is the only candidate who really takes global warming seriously.

Gore has advocated a carbon tax, which imposes a levy on entities that emit carbon dioxide into the air, to reduce greenhouse-gas emissions. He is correct in his analysis that increasing the price of carbon-based fuels is the most reliable way to begin fixing the problem.

A carbon tax forces energy consumers to consider the costs of their emissions on the environment, addressing a serious market externality. Furthermore, carbon tax revenue can be used to reduce tax rates on other things, perhaps even improving the overall efficiency of the U.S. economy.

`Cap and Trade'

Clinton and the other Democrats favor a regulatory ``cap- and-trade'' approach, which provides economic incentives for polluters to reduce emissions. There are many problems with this plan that have become increasingly apparent as economists studied it more closely. A growing body of literature suggests that a cap-and-trade system will either be ineffective, in which case it will do little harm to the economy, or effective, in which case it will devastate the economy.

The odds are that cap and trade will be ineffective, which might make an economist happy, but should keep a global warming pessimist up at night.

A political cynic might add that Clinton's support for cap and trade is a product of political expediency. A carbon tax would dramatically increase the price of coal and likely have a negative impact on key swing states such as West Virginia, Pennsylvania and Ohio. Cap and trade would be much less likely to create a stir in those areas.

But once cap and trade is adopted, the political impediments to instituting a carbon tax will surely become overwhelming, making real progress on global warming impossible. On the issue that Gore cares the most about, our nation is at a crossroads. It's hard to imagine a bigger incentive for him to run.

Good for the Party

From the point of view of the Democratic Party, a Gore run is a big plus as well. The biggest consideration is the effect on the Republican nomination. If Clinton is nominated in a cakewalk, then moderate Democrats and independents will flock to Republican primaries, which look as if they will be hotly contested. That flow of moderation in the Republican direction would increase the odds that Democrats would face a more broadly popular opponent in November 2008.

The main downside of a Gore campaign is that he has reached a global superstar status that rivals sainthood, and his image would take a big hit if he ran and lost. If Gore is serious about global warming, that risk would seem a small price to pay for entering the race.

To contact the writer of this column: Kevin Hassett at khassett@aei.org