Scott Jennings, a CNN contributor, is a former special assistant to President George W. Bush and former campaign adviser to Sen. Mitch McConnell. He is a partner at RunSwitch Public Relations in Louisville, Kentucky. Follow him on Twitter @ScottJenningsKY. The opinions expressed in this commentary are his own.

(CNN) New polling from CNN and other outlets indicates that President Donald Trump's job approval has improved since mid-December, and that the Democrats' advantage over Republicans in the upcoming midterm elections has shrunk.

Scott Jennings

The reasons are obvious -- the Republicans cut taxes, the economy is good, and people largely approve of Trump's moves to break the logjam with North Korea. Basically, people like peace and prosperity. Or, as philosopher and fictional minor league baseball pitcher "Nuke" LaLoosh once opined : "I love winning, man. ... It's like better than losing."

The danger for Republicans, of course, is that peace and prosperity won't be enough to overcome the head winds they face. History is not on their side, as the party in power almost always loses seats in a president's first midterm. And Trump, despite the polling improvement, still carries a job approval well below what any GOP strategist would tell you is necessary to overcome history.

Polling averages today put Trump between 41% and 42%, depending on which tracker you use (and whether you look at polls of voters or mix in surveys of adults, not all of whom are registered to vote). By comparison, let's look at Gallup job approval numbers for President Barack Obama in the four polls leading into the 2010 midterm in which Republicans walloped the Democrats: 46, 45, 44, 45

So even as Trump improves, Democrats should feel good that he has not improved enough to reach a level that would help his party overcome history. There are structural problems in the surveys (chiefly the gender gap) that might hold down Trump's ceiling as he continues to struggle mightily to gain the support of non-Republican women.