Since the Second World War, history shows 100% chance of rallying after the mid-term elections

A long-time market observer on Wall Street encourages investors.

Last month, the S & P 500 lost more than 6%. During this period, its lowest closing level was reached on Monday at 2641, and has risen by almost 4% since then.

Detrick pointed out that the recent slowdown was not unusual. In an intermediate year, its data show that the S & P 500 index has always been negative early October.

"Look at the last elections we had, mid-term in 2014: we had a big sale in mid-October, then a hollow, then a rally," he said, adding that almost all Yearly gains had been made in the last few months of the year.

Once Tuesday's end-of-session work is over, he said, seasonal workers will dominate the market. It 's at this time that a "surprise" end – of – year gathering could take over, according to Detrick.

"This October 29 trough, especially with the strength we've seen over the past few days, could really be a pretty big trough," said Detrick.

– Keris Lahiff from CNBC contributed to this article.