These charts reflect the results of a recent Politico / Morning Consult Poll -- done between September 6th and 9th of a national sample of 1,988 registered voters, with a 2 point margin of error.
Like several other polls, it shows the Democrats with a double-digit lead (10 points) on the generic ballot (45% to 35%). One reason why this is true (other than the unpopularity of the Republican in the White House) is the public's opinion on the two parties in Congress.
While the voters are enamored of either of the congressional political parties, they dislike Republicans significantly more than Democrats. The Republicans have a 22 point more unfavorable than favorable difference, while the Democratic difference is only 8 points.