The poll trend has brought the Republicans renewed hope that they can hold the House of Representatives as well as the Senate at the mid-term elections in November.
Speaking to Republican congressmen last week, Trump said: "You folks have done well. I just looked at some numbers. You've even done better than you thought."
Some 40 per cent of Americans now approve of the job he is doing, according to a poll of polls by FiveThirtyEight.com. That is up from around 37 per cent before Christmas.
While most US voters still disapprove of his presidency, the last time Trump hit 40 per cent approval before the turn of the year was May 2017.
Similarly the Democrats' lead over the Republicans in how people will vote in congressional races has dropped dramatically in the last month.
The Democrats held a 13-point lead on Christmas day, according a poll of polls from RealClearPolitics.com, but that is now down to just 6.6 points.
It comes despite Trump facing a string of scandals in January, including the publication of the tell-all book Fire and Fury, which painted him in an unflattering light.
Trump also faced claims an affair with an ex-porn star had been covered up by his lawyer – he denied the encounter – and a backlash for reportedly criticising immigration from "shithole" countries.
Credit for the improving polls has been given to the economic achievements that Trump has been quick to tout since he entered office.
The American economy grew at an annual rate of 3.3 per cent in the third quarter of 2017 – quicker than at any time in the last three years.
The US stock market has also hit record highs, though the falls in recent days have dented that achievement.
There are signs that Trump's US$1.5 trillion tax cut, which polls suggested was opposed by most people when it passed in December, is now seen more positively from voters.
Some recent polls have had as many Americans approving of the tax bill as disapproving – though the results remained mixed.
The changes have checked the Democrats' momentum for the midterms created by their shock Alabama Senate win just before Christmas.
Trump supporters stand across the street from Trump protesters, in Blue Ash, Ohio, before President Donald Trump's visit today. Photo / AP
They need to win around 24 seats from the Republicans to gain control of the House of Representatives – a result that still seems possible on the current polls given historic trends.
However internal splits between moderates and hardliners about how hard to fight Trump on immigration and other issues continue to rumble on.
The Democrats face a harder task in winning back the Senate, despite the Republicans holding just a 51-49 majority, because they have far more senators facing re-election.
Trump is expected to focus relentlessly on the growing economy and job creation, as he has done over the last year, in the run-up to the midterms.
In his State of the Union speech last week, Trump spent much of the opening section listing statistics to back up his claim that he has turned the American economy around.
Critics say that he inherited a healthy economy from his predecessor, President Barack Obama, and that the sharp increases in the stock market have not been matched in real wages.
Trump’s culture warrior persona is the essence of his political appeal. Without it, he’d just be a billionaire cutting taxes for billionaires, writes @mattyglesias. https://t.co/TP4Ep25TzD
