Since records began with Eisenhower's inauguration in 1953, no incoming president has had an approval rating below 50% at the start of his administration. Reagan and George HW Bush came in at 51%, and both managed to improve (to 68% and 56%, respectively) in the first 100 days. Even George W Bush, despite the taint surrounding his election, came in at 57% and inched up to 62% by April 2001.
And along comes Trump. A Quinnipac poll released today has him at 37%, and falling. As Josh Marshall puts it, "Trump, his agenda and his party are deeply unpopular. Indeed, Trump's gotten steadily more unpopular over the last four weeks. All of this tells us that political gravity still exists. Indeed, it is already shaping events on Capitol Hill."
For comparison, shortly before he left office under a pall of sex scandals and rampant corruption, Italy's Silvio Berlusconi polled between 33-35%. And immediately before the watershed UK election in 2010, the Labour Party under Gordon Brown polled around 30%. And in 2015, just before losing to Justin Trudeau, Canada's Stephen Harper polled around 33%.
In other words, Trump is coming into office approximately as popular as discredited and failing leaders of other modern democracies right before their defenestrations.
It'll be interesting to see if he notices.