The S&P 500 has been down two-thirds of the time in the first years of all Republican presidential terms since World War II, whether it was the first or second term. The index, in those years, averaged a 1.8 percent decline.

That's because stocks have underperformed in the first year of Republican presidents most of the time, according to CFRA data.

Pundits say it all the time. Donald Trump is not like any ordinary Republican president. That may prove to be a good thing for the stock market in 2017.

As for Republicans, the performance was even worse when it was the first year of the first term of a GOP president. In those five instances, the S&P 500 was only up once and the average loss was 2.7 percent.

That compares with big first-year gains in Democratic terms. The S&P 500 averaged a 17 percent first-year advance, and the market was up 89 percent of the time in the first year.

Wall Street strategists certainly are not forecasting a decline in stocks for 2017, and many see the between 2,300 and 2,400 next year. A few, like RBC's Jonathan Golub see the S&P reaching 2,500 by year-end. The S&P 500 was just under 2,250 on Thursday.

Sam Stovall, CFRA's chief investment strategist, said the theory has been that Republicans inherited a mess made by Democrats, but instead it may be a matter of timing. Every Republican president since Teddy Roosevelt has had a recession in their first term. Richard Nixon and George W. Bush had two while in office.

Stovall said the market moved in advance of those recessions in the first year of the term. "History says be careful, that traditionally recessions have accompanied Republican administrations. Not necessarily because they do things wrong, but they probably just had bad timing," he said.

There are no expectations for a recession in 2017. In fact, JPMorgan last week said its preferred metric for recession probability showed just a 23 percent chance in the next 12 months, down from a 30 percent chance in October.

Trump also has so far been positive for the stock market, with his promises of corporate tax reform, less regulation and a big fiscal spending program spurring a sharp jump in stocks since the election. But some strategists say the market gains from those programs may have been pulled forward, and 2017 could be a year where the market moves up but with less force as it looks for progress on those plans.

Stovall expects the S&P to reach 2,335 next year. "I'm a little skeptical about the enthusiasm investors have toward what a Trump administration can do," he said. Stovall said it may be difficult to get a big infrastructure spending bill past the Republican Congress, which would be unlikely to approve a lot more spending if it's based on debt.

The roughly 10 percent gain in the S&P 500 so far this year also goes against the grain of market history, which shows that Democrats, in the final year of their second term see stock returns lower than the third year. A second-term Democratic president's fourth year has averaged a gain of just 1.2 percent.



The best year for a presidential term for both parties has been the third year, with the S&P up 88 percent of the time with an average gain of 16.1 percent. While President Barack Obama's final year is outperforming that of the average Democrat, his third year way underperformed the average 11.8 percent gain seen in a second-term Democratic president's third year. The S&P was lower in 2015, ending the year with a slightly less than 1 percent decline.

"In the third year, you've got the party in power wanting to stay in power, and they try to inject stimulus that would cause the economy to grow, and make the electorate happy," said Stovall. "That's why nothing happened in the past two, third years. There was no stimulus. That's why we were down both times. The first two times in history that we were down in that third year."

The S&P was just barely lower in 2011, down less than 0.1 percent.