The chart above is from the Gallup Poll -- done between January 21st and February 2nd of a national sample of 905 adults, with a 6 point margin of error.
It shows the popularity of the Republican Party has slid since Election Day. In October, the difference between the Republican and Democratic Parties was only 1 point, and in November was only 2 points. That's not a significant difference.
But since the election, the Republicans have opted to support Donald Trump and his ridiculous lies about the election -- and that has caused public approval of them to drop several points. There is now an 11 point difference in public approval (Democrats 48% to Republicans 37%).
The GOP would have been better served to cut Trump loose and defend our democratic system. Their refusal to do so will not help them.