For this question, I went through the S&P index data and also tried to find out the dates when Trump announced/implemented tariffs and compared the index value the day before and the day after to arrive at a base rate. I went through the following wikipedia article to collect the information:

First term tariffs:

• January 23, 2018 – Solar Panels and Washing Machines.
• On March 1, 2018, Trump announced his intention to impose a 25% tariff on steel and a 10% tariff on aluminum imports. On March 8, he signed an order to impose the tariffs effective after 15 days.
• On March 22, 2018, Trump signed a memorandum under the Section 301 of the Trade Act of 1974, instructing the USTR to apply tariffs of $50 billion on Chinese goods. 
• On April 3, 2018, the U.S. Trade Representative's office published an initial list of 1,300+ Chinese goods to impose levies upon.
• On April 4, 2018, China's Customs Tariff Commission of the State Council decided to announce a plan of additional tariffs of 25% on 106 items of products.
• In an announcement on May 31, 2018, Canada, Mexico, and the EU became subject to the steel and aluminium tariffs.
• On June 15, Donald Trump released a list of $34 billion of Chinese goods to face a 25% tariff, starting on July 6.
• Another list with $16 billion of Chinese goods was released, with an implementation date of August 23.
• On August 1, 2019, that he would impose a 10% tariff on $300 billion of Chinese imports beginning September 1.
• On December 2, 2019, President Donald Trump reinstated steel and aluminium tariffs against Brazil, later backed down, and Argentina.

I also considered the second term tariffs to arrive at a base rate of 56.52%.

Market went up 13 out of 23 times (56.52%).