DETROIT — President Joe Biden’s support is on shaky ground in Michigan, and he trails Republican Donald Trump by 8 percentage points in a head-to-head matchup 10 months before the Nov. 5 election, according to a new statewide poll commissioned by The Detroit News and WDIV-TV. The survey of 600 likely general election voters in the battleground state found only 17% said Biden, the Democratic incumbent, deserved another term leading the country. That number marked a low for a major public officeholder in modern Michigan political history, said Richard Czuba, founder of Lansing-based Glengariff G…