Of the last five generic ballot polls taken, four show the Dems’ lead cut in half from the heights of mid-December, when they were leading consistently by margins of 10 points are better. If you missed this post on Friday night about NBC’s latest survey, that’ll catch you up on the other numbers. The most dramatic example of the trend towards Republicans comes in today’s new one from CNN, which has Republicans trailing by just five points among registered voters. A month ago, CNN had Republicans down … 18. No typo. Eighteen points on the generic ballot, when usually a lead of eight or nine is enough to signal a major midterm wave on the horizon. That 18-point lead in December was the largest margin notched by any generic ballot poll in 2017 tracked by RCP and might well have been the largest in many years. And now, in the span of 30 days or so, more than two-thirds of that lead is up in smoke. Thanks, tax cuts!

Don’t get too excited yet, though. There’s a catch. Actually, two catches.

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…

The tightened race among voters more broadly reflects shifts among independent voters in the last month, who broke heavily in Democrats’ favor on the generic ballot in a December poll conducted amid Republican efforts to pass an unpopular tax bill. In the new poll, independents have grown more positive toward Donald Trump, and now split almost evenly on the generic ballot: 45% for the Republican in their district to 42% for the Democrat.

A month ago, with the GOP majority in Congress having passed nothing substantial after nearly a year in power, Republicans were demoralized. A month later, tax cuts passed and the good economic news keeps rolling in daily. It’s amazing what an accomplishment can do to lighten the electoral mood.

About those catches, though. Catch number one: Although the race has tightened among registered voters overall, it hasn’t tightened among the voters who are most enthusiastic to vote. Among that group it’s still a bloodbath in the making, with Democrats leading by 15 points. The trick to surviving the midterms for the GOP is to figure out a way to get their own ambivalent voters to the polls while keeping the Dems’ at home. A great economy might accomplish the latter. Will it accomplish the former?

Catch number two: Er, although it’s true that four of the last five generic ballot polls have been good news for the GOP, the fifth one is a doozy. New from ABC/WaPo:

Democrats have solidified their position in the November midterm elections in the latest ABC News/Washington Post poll, maintaining a 12-point lead among registered voters while improving to a wide 14-point advantage among likely voters in congressional preference.

Democrats typically lose support in the shift to likely voters, given lower turnout among their stalwart groups. That’s not the case now: Among those most likely to vote, 54 percent support the Democratic candidate in their congressional district, compared to 40 percent for the Republican.

This double-digit Democratic lead among likely voters compares with a dead heat in this group in early November. One factor: They’ve locked down their base, including party identifiers, women and minorities.

Most major pollsters now see leads of five to six points for Democrats on the generic ballot. ABC/WaPo sees a margin twice as large, and importantly, it sees an even wider margin among likely voters. If you follow national electoral polling, you know the rule of thumb: The total population leans Democratic, the subset of the population that’s registered to vote is a bit more balanced but still Democratic-leaning, and the subset of registered voters who say they’re likely to vote in an upcoming election are more balanced still. In midterms in particular Republicans have used their greater enthusiasm over the last few cycles to swamp Democrats at the polls despite the latter’s numerical superiority in the overall population. The trend this time is different. The one thing in common between the CNN poll that’s hopeful for Republicans and the ABC/WaPo poll that’s predicting a slaughter is that both polls see greater enthusiasm to vote on the left than on the right. Which is not surprising, as the out-party typically is revved up to send a midterm message to the White House and Trump is broadly unpopular to begin with. But it’s an asterisk on all of the polls showing the generic ballot tightening. Republicans have crept closer among registered voters but how many of those voters on each side are actually going to the polls in November?

One other point in common between the two polls is the enormous lead Democrats hold among women. CNN has Dems ahead among females 59/35 while ABC/WaPo has it 57/31, noteworthy consistency among two surveys that otherwise diverge. If Republicans get swamped this fall, odds are good that it’ll be because of heavy support for Democrats among women. Among white women in particular, support this year is a mirror image of what it was four years ago when Republicans destroyed the Democrats in the midterm. That year the GOP won by 14 points among white females; this year Democrats lead by 12 within the group. If that holds up, it’ll be laid squarely at Trump’s feet afterward.