It was a dismal year for Republicans, as polls consistently showed the party trailing Democrats in national generic congressional ballots.  Last month, the gap between the parties was 18 points in the CNN poll, with double-digit leads by Dems in other polls.

On top of that, the so-called "enthusiasm gap" heavily favored the Democrats.  Their voters seemed more excited, and thus more likely, to vote in November's midterm elections.

The numbers were latched on to by national pundits as proof that a Democratic wave was building that would sweep the party into power.

But something has changed in the last month.  Republicans passed a massive tax cut and despite Democratic efforts to disparage it, independents and Republicans have apparently embraced it.  The gap between the parties on the congressional generic ballot has narrowed in the CNN poll from 18 points to 5 and Republicans are far more enthusiastic about voting than they were just a month ago.

The new poll's 49% Democrat to 44% Republican margin among registered voters is almost identical to Democrats' standing in January of 2006, the last midterm election year in which they made significant gains in the House of Representatives.

But it represents a large shift from CNN polls conducted in the past three months, in which Democrats held double-digit advantages over the Republicans.  Preferences among all adults have shifted less dramatically, but are also tighter than last fall, with Democrats currently 10 points ahead of Republicans among all Americans.

Polling all Americans is a useless exercise, especially for a midterm election, where turnout will be between 25 and 30%.  Polling registered voters is more accurate but falls short of polls that include only "likely voters." 

Enthusiasm about voting in this year's contests has grown as the calendar page has turned, with a spike among Republicans and Republican-leaning independents from 32% feeling extremely or very enthusiastic about casting a ballot in December to 43% saying the same now.  Democrats still hold an advantage in enthusiasm, however, with 51% saying they are that enthusiastic about voting in this year's midterm elections.

Enthusiasm for this year's contests peaks among liberal Democrats, 62% of whom say they are deeply energized about voting.  Among conservative Republicans, just 46% say the same.

That disparity is fueling the Democrats' much wider edge on the generic ballot among enthusiastic voters.  Among those voters who call themselves extremely or very enthusiastic about casting a ballot, 56% favor the Democratic candidate in their district, while 41% favor the Republican.  Republicans hold a 5-point edge among those voters who rate themselves somewhat enthusiastic or less.

The "enthusiasm gap" matters.  While not a guarantee of voter sentiment about casting a ballot on election day, the numbers reflect the reality that voters for the party out of power are eager to change that, while voters belonging to the party in power are less so.  This is reflected by historical results that show that the party that holds the White House loses a significant number of seats in the first midterm election.

Party partisans are going to vote regardless of how "enthusiastic" they are.  Far more significant are GOP gains among those who are slightly less enthusiastic.  They are the persuadables, and with the right message and competent voter outreach, they will be the ones who determine whether the GOP stays in power or is thrown out.

Trump's relative unpopularity will be a drag, and the Democrats will do everything they can to nationalize the election.  But there's one big ingredient missing for Democrats: a national issue.  In 2010 and 2014, Republicans had Obamacare to run against.  The Dems will try to run against the tax cuts, but with just about everybody getting more money in his pocket because of them, the Dems aren't likely to succeed.

And, against all polling expectations, things are beginning to improve for Trump.  Despite massive negative media since he took office, his approval stands between 40% and 45%.  Those numbers have been slowly climbing over the last month.

Recent individual state polls are hard to come by, but a surprising result in sky-blue Minnesota should fuel more optimism for Republicans.

Star Tribune:

The Star Tribune's first election year poll is complete and, all things considered, it was a good series of results for Minnesota Republicans.  President Donald Trump's job approval came in at 45 percent.  His 2016 Minnesota tally: 44.9 percent.  [This] means [that] after one of the most tumultuous first years in recent presidential history, if Trump lost supporters here, he must have gained an equal number.  He was especially strong in the suburbs and in greater Minnesota, which could mean help for Republicans like U.S. Rep. Jason Lewis and GOP state lawmakers in the suburbs where Trump's support remains strong.

It may seem strange that a president's approval rating would be crucial to a contest in which he is not on the ballot, but history bears out a strong correlation.  The president's party loses an average of more than 36 seats in Congress when his approval is below 50 percent.  But Trump's number in Minnesota does not foretell the kind of election wave that many Democrats are hoping for.

That's the bottom line.  Democratic hopes for a massive victory next November were fueled during the fall by horrible numbers for Republicans.  But as this and other polls suggest, those hopes may have been transitory.  The GOP is likely to lose some seats, given the number of Republican House members retiring and some districts held by the GOP turning bluer.  But the outlook today gives the Republicans a decent chance to hold on to the House – something few would have considered just a few short months ago.