The key there is "trends'
As we all know, there will be another poll tomorrow, and another one the day after that, wait long enough, or work hard enough, and you will find one to support your opinion
With the election over two years away, polls today are pretty much strictly for conversation, two and half years is an eternity in politics. Plus, incumbents, until they have an actual defined opponent, generally look bad going into the election
11/14/2018
"As speculation for 2020 begins to heat up, a little more than 3 in 10 Americans want to see President Donald Trump win a second term in the White House, according to a new poll. A Monmouth University poll out Wednesday found that though the president’s approval rating stands fairly steady at 43 percent, only 37 percent of registered voters want to see him reelected"
https://www.politico.com/story/2018/11/14/poll-trump-2020-reelection-support-990015