Not entirely true, Atlanta runs as no partisan but the council is clearly all Democrats. Democrats endorse them. Same with San Francisco. Here are a few cities that allow party affiliation: Seattle 8 Democrats, no Republicans and 1 Socialist Party. NYC 46 Democrats 3 Republicans 3 open seats. Baltimore 15 Democrats no Republicans. Minneapolis 13 Democratic Farm Labor Party 1 Green Party. Chicago 46 Democrats 4 Independents no Republicans, Oakland, 8 Democrats no Republicans. Detroit 8 Democrats 1 Vacant seat. Los Angeles 13 Democrats 1 Independent. Houston 11 Democrats and 5 Republicans
Twelve cities picked randomly, St. Louis, Atlanta, Dallas, San Francisco however they have non-partisan elections.
The other eight cities tallied 168 Democrats, 8 Republicans (5 from Houston), 1 Green Party, 1 Socialist, and 5 Independents.
That is hardly bi-partisan, the Democrats do as they please in most cities.