The state of Ohio has long been seen as a crucial state, and no Republican has been elected President without winning Ohio, including Donald Trump in 2016.
So only Gerald Ford has been a Republican President and lost Ohio, when he ran for a full term against Jimmy Carter in 1976. Once we knew that Carter had won Ohio, it was clear Ford would not have a full term, after succeeding the resigned Richard Nixon in 1974.
When one looks at party history since the Republican Party was founded in 1854, we find only five elections in which the Republican candidate lost Ohio to a Democrat, as follows:
John C. Fremont 1856 lost to James Buchanan
James G. Blaine 1884 lost to Grover Cleveland
President Benjamin Harrison 1892 lost to former President Grover Cleveland
Thomas E. Dewey 1944 lost to President Franklin D. Roosevelt
Richard Nixon 1960 lost to John F. Kennedy
So only three Democratic Presidents have won the White House without winning Ohio–James Buchanan in 1856, Grover Cleveland in 1884, and John F. Kennedy in 1960, with Cleveland second time and FDR fourth time winning a return to the White House without winning Ohio.
Right now, polls show Donald Trump winning Ohio by 5 points instead of the 8 point lead he had over Hillary Clinton in 2016.
So if polls hold up, Joe Biden will be the fourth Democrat to become President without Ohio, only the sixth time in 166 years, and the first time since 1960.
Ohio has been steadily losing electoral votes, as the balance of population has moved South and West, and will likely lose one electoral vote in 2024 and 2028, going down from 18 to 17, so will have less impact politically in the future!