The scheduled vote Monday by the Charlotte, N.C., city council on final approval for its bid to host the 2020 GOP convention is turning into an unexpected cliffhanger, with liberal council members facing mounting pressure not to host President Donald Trump’s expected nomination for a second term.

Democratic Mayor Vi Lyles pledged the city's support last spring when Charlotte entered what would prove to be the winning bid with national Republicans. She said Charlotte should be a place of inclusion, not exclusion.

“The...