The first Party ID surveying in 2018 has shown a big move for Democrats in a year they're looking to regain control of Congress. The last time Democrats had a ten-point advantage in party ID was in October of 2013 - that is until now. As recently as December, Democrats only held a 2-point advantage in pledged party support. That ballooned to a ten-point advantage in January. Here's the latest from Gallup:
Democrats: 32% (+5% over December)
Independents/Third Party: 44% (-2% over December)
Republicans: 22% (-3% over December)
Independents are still a majority by plurality, but Democrats had a huge month rally support to their ranks. It's notable that 3% of pledged Republican support didn't just defect to the Independent column (which is what's most common when a declared partisan becomes frustrated with their political party) but actually shifted to the other party along with 2% of those who were undeclared previously. It's worth noting that this work was done prior to the impact of tax reform being felt which might make a difference by the time February's results are produced - but it's also significant that Democrats are currently the best positioned they've been politically since the fall of 2013 - just in time for the mid-term election cycle. If Democrats hold this kind of advantage by November, they'll almost certainly reclaim control of Congress. The last time Democrats regained control, in 2006, they had an 11-point advantage on Election Day.