WASHINGTON (CNN) Democrats' already wide advantage over Republicans in a hypothetical Congressional matchup has grown, according to a new CNN poll conducted by SSRS . At the same time, enthusiasm about voting next year has increased among Democrats nationwide following an unexpected win in Alabama's Senate special election and a strong showing in Virginia's state government elections last month.

Among registered voters, 56% say they favor a Democrat in their congressional district, while 38% prefer a Republican. That 18-point edge is the widest Democrats have held in CNN polling on the 2018 contests, and the largest at this point in midterm election cycles dating back two decades. The finding follows several other public polls showing large double-digit leads for Democrats on similar questions.

Independent voters favor Democrats by a 16-point margin, 51% to 35%, similar to the 50% to 36% margin by which they favored Democrats in fall of 2005, ahead of Democrats' 2006 recapturing of the House and Senate. The Democrats hold a larger lead overall now because Republicans make up a smaller share of the electorate than they did in 2005

And those Republicans who are still in the electorate are less enthusiastic about voting next year than Democrats. Overall, 49% of registered voters who are Democrats or Democratic-leaning independents say they are extremely or very enthusiastic about voting for Congress next year, compared with 32% of Republicans and Republican-leaning independent voters who say the same.

The poll was conducted before the passage of Republicans' signature tax reform bill this week, which the GOP hopes will boost their electoral prospects next year. Findings from the same poll released earlier this week found that the bill's unpopularity on the rise, with few expecting tangible benefits for themselves once it becomes law.

The Republican Party itself is viewed less favorably than the Democratic Party. About a third -- 34% -- have a favorable view of the GOP, while 46% say the same about the Democrats, according to the poll. That marks a rebound for Democrats after their favorability ratings sagged earlier this fall and is the highest mark for them since July of 2016. The Republican numbers are also on the rise, but remain below levels reached earlier this year.

The GOP may be further held back by a public displeased and angry with the way the country is being governed under their control. Overall, 68% say they are dissatisfied with the way the nation is being governed, and a matching 68% say they are angry about the way things are going in the country today.

Those numbers are similar to the levels seen in December 2015, ahead of the 2016 presidential election in which voters seeking change propelled Donald Trump to the presidency. But the partisan divides underlying those numbers are now largely reversed.

About two-thirds of Republicans say they're satisfied with the way the nation is being governed now, up from 10% in 2015, when Barack Obama was president and Republicans controlled the Congress. Among Democrats, satisfaction has fallen from 40% to 6%. Independents remain about equally unsatisfied: 25% are now vs. 22% in 2015.

Anger, too, has switched sides, with half of Democrats now saying they are "very angry" about the way things are going in the US, up from 14% in 2015. Among Republicans, deep anger has dipped from 41% in 2015 to 10% now.

And on that change voters were seeking in 2016, most say Trump did bring it: 77% say his presidency has created significant changes in the country, but more say they're for the worse (43%) than for the better (30%). Back in 2009, fewer thought Obama had brought change by November of his first year in office (69%), but by a 40% to 27% margin, they said those changes were for the better rather than the worse.

Trump himself continues to garner deeply negative favorability ratings -- 36% hold a positive view, 60% a negative one -- and his approval rating for handling the economy has reached a new low, despite the White House's frequent touting of the country's economic progress. Overall, 49% disapprove of Trump's handling of the economy, the highest level to say so since he took office, while 44% approve.

House Speaker Paul Ryan's favorability ratings have ticked upward from their low point in mid-September, but he remains net negative, 35% favorable to 45% unfavorable, as midterm elections approach. The Speaker does earn net-positive ratings among his own partisans: 66% have a favorable view, 19% unfavorable. But his numbers lag behind Trump's ratings among the Republican laity, 85% of whom have a positive view of the President.

Ryan has been circumspect in discussing his own political future in the face of a pile of daunting poll numbers, saying in an interview this morning on ABC's "Good Morning America" that "It's not even 2018 yet ... (Running for reelection is) something (my wife and I) haven't discussed yet. Something we'll discuss down the road when the appropriate time comes."