President Donald Trump's approval ratings are hovering under 30 percent in Michigan, according to a survey released Friday by Michigan State University.

MSU's State of the State Survey, issued periodically by the university's Institute for Public Policy and Social Research, found 28 percent of survey respondents rated Trump "excellent" or "good" when asked to rate Trump's job performance. 51 percent of survey respondents gave Trump a "poor" rating, MSU professor and State of the State director Charles Ballard said.

The survey was comprised of 954 Michigan adults interviewed on landlines and cell phones between April 19, 2017 and July 30, 2017. The survey's margin of error was +-3.17 percent.

Ballard said Trump's favorable ratings decreased over the course of the survey, dropping from 31.5 percent favorable in April to 20.4 percent favorable in July. Over that same time period, his "poor" ratings rose from 46.1 percent to 59.4 percent.

"This survey was taken in late spring and early summer at a time when Trump was unable to score significant legislative achievements, and when his White House often appeared to be in disarray," he said.

Ballard said Trump still retains strong support among Republicans, with 59 percent of self-identified Republican survey respondents giving him an "excellent" or "good" approval rating.

The survey also found Gov. Rick Snyder's ratings have improved slightly since the last State of the State survey, coming in with 29.3 percent favorable reviews compared to about 25 percent favorable ratings following the Flint water crisis. Ballard said Snyder has gotten favorable ratings of 34 percent or higher during most of his time in office.

In addition, survey respondents seemed to have a more upbeat attitude about the economy -- 62 percent of survey respondents called their finances good or excellent, the best numbers recorded by the State of the State survey since 2002, Ballard said.

To read more about the State of the State survey results, visit MSU's Institute for Public Policy and Social Research website.