No question, President George Bush’s approval ratings have "pulled an Enron."

A recent Associated Press-Ipsos poll conducted June 12-16 showed only 29% of the public gave Bush a favorable rating. It’s the least favorable approval rating for a U.S. president since Jimmy Carter’s approval rating dropped to just 22%.

While that lousy view of the job Bush is doing will help set up a more contentious election in November, here’s a curious fact that investors will find quite rewarding:  The key to better stock market returns isn’t having a president we “love” – it’s having a president that we don’t quite hate.

Let me explain.

According to a study of presidential approval ratings by Ned Davis Research that looks back all the way to the days of President John F. Kennedy, when the president’s approval rating is below 35%, as it is now, the Dow Jones Industrial Average Index loses an average of 5.9% per year. When times are good and presidential approval ratings exceed 65%, the Dow rises at an annualized rate of 2.6%. But when just 50%-65% of the public gives a favorable rating, the markets do a bit better and the Dow rises at a 5.4% annualized clip. (Click here for the full chart on how the Dow has performed during different presidential administrations.)

Now here’s the really interesting part.

When the majority of Americans disapprove of how the president’s doing his job, and the approval rating clocks in between 35% and 50%, the Dow posts an average annualized gain of 12.3%. In other words, when less than half the population has a favorable view of a sitting president’s performance, the Dow’s upside potential improves by 127.78%.

Talk about a counter-intuitive result!

For next year, then, it seems that the key isn’t for us to elect a president that everybody likes; instead, the country needs to elect a president that the masses “hate” a bit less than they dislike Bush and who only does his job well enough to garner the support of between 35% and 50% of the population.

Anything worse and the Dow could fall, which, given “The Dubya’s” current lackluster rating, is right on track for how the markets are behaving lately.

And that has us thinking: Who amongst the presidential contenders that are left do we like the least?

[Editor’s Note: This story is part of Money Morning’s ongoing “Election 2008″ series covering the investing impacts of the presidential campaign. Contributing Editor Martin Hutchinson has personally interviewed the economic advisors for candidates McCain, Obama, and John Edwards and concluded that Obama and McCain would be the best candidates for investors. For a full report on the “presidential profit plays” that was derived from Hutchinson’s research, please click here. The report is free of charge.]