The historical trend doesn't overwhelmingly favor one party over another. But keep this in mind: The election is probably having its greatest influence on Wall Street right now. Investors don't like uncertainty, whether it's uncertainty in elections, earnings or anything else. Presidential polls that show a narrowing gap between the candidates give Wall Street palpitations.

That's good for investors who can run contrary to the crowd.

I've always believed that you should use the market's weakness to do some buying. If you've been saving some extra cash, you may want to deploy it as the campaign heats up. When the furor dies down after the election, Wall Street will once again focus on interest rates and earnings, the two factors that have more to do with where stocks go than anything else.

No matter which candidate finally wins, you can rest assured that there will be a much greater focus on economic issues for the next few years than there has been in the previous few. And that, ultimately, should be good for the market and investors (see also, "Presidential Profits for Your Portfolio.")

Here are but a few of the many statistics used to bolster the case for a bull or bear market based on the election outcome. If the findings prove anything, it is that statisticians from both political parties can claim bragging rights to the stock market's long-term gains.

Why It Pays to Elect a Democrat

Since 1901, the Dow Jones Industrial Average has risen at an 8.5% annual rate under Democratic presidents. (Up only 6.4% on average under Republicans.)

Since 1926, the S&P 500 has risen an average 14.9% under Democratic administrations and has gained an average of 20.9% the year after an election where a Democrat succeeds a Republican. (Up just 9.7% on average when Republicans have held the White House and 11.6% when a Republican replaces a Republican in the White House.)

Real GDP under Democratic presidents has risen...