The U.S. government shutdown is eroding consumer sentiment among Republicans concerned about the closure while having little impact on already-weak confidence for Democrats and independents, according to a University of Michigan survey.

While 9 percent of Republicans spontaneously mentioned the shutdown this month compared with 20 percent of Democrats, those Republicans had a sentiment index 34 points lower than fellow Republicans who didn't mention the shutdown.

That compares with a 1-point gap between Democrats who did and didn't mention the shutdown, the university said Friday in a special report based on its monthly survey of Americans.

For Democrats, the shutdown “could not make their expectations any worse than how they already viewed economic conditions under the Trump administration,” survey director Richard Curtin said in the report.

“In contrast, among Republicans, who generally held much more favorable levels of confidence, references to the shutdown made a relatively large difference.”

The university said last week that its preliminary U.S. consumer sentiment index for January fell to 90.7, the lowest level since Donald Trump's election in 2016.