But fewer people are getting refunds this year and that's causing angst for Republicans who want to convince voters that the 2017 tax overhaul really did give them a tax cut. If middle America can't be persuaded, it could have big implications for the long-term viability of the overhaul, and how consumers spend their extra income.

Republicans are on the defensive. The once little-noticed ritual of releasing weekly refund data during the tax filing season has become politically fraught, with unfavorable data being released late on a Friday night, and better figures a week later causing Treasury Secretary Steven Mnuchin to take to cable news to tout success.