Joe Biden has won the state of Wisconsin, a key swing state in the race for the presidency, AP projects.Why it matters: Biden's flip of the state's 10 electoral votes further narrows President Trump's potential paths to victory — and bodes well for the former vice president's prospects in the outstanding Rust Belt battlegrounds of Michigan and Pennsylvania.Trump's narrow 2016 victory in Wisconsin helped pave his path to the White House.Biden was leading in the state by 8.4 points the day before Election Day, according to FiveThirtyEight's average of polls.This story is developing. Please check back for updates.Editor's note: This post was corrected to show that Biden was up in Wisconsin by 8.4 points (not by 8.4%).