A Democratic congressman on Friday invoked the era of slavery to criticize former New York City Mayor Rudy Giuliani (R) for saying he didn’t think President Barack Obama “loves America.”

Rep. Stephen Cohen (D-TN), who represents a majority-black district, tweeted that perhaps the former mayor thinks Obama loves America “3/5 as much as Giuliani & his pals.”

Rudy Giuliani questioned how much,or even if, President Obama loves America.Maybe he thinks he loves it 3/5 as much as Giuliani & his pals — Steve Cohen (@RepCohen) February 20, 2015

Cohen was referring to the three-fifths compromise reached at the 1787 Constitutional Convention, which allowed states to count each slave as three-fifths of a person toward determining its population and thus its representation in Congress. The rule was effectively repealed by the Fourteenth Amendment.

Giuliani told the New York Times on Thursday that his comments couldn’t be construed as racist because Obama’s mother was white.

“Some people thought it was racist — I thought that was a joke, since he was brought up by a white mother, a white grandfather, went to white schools, and most of this he learned from white people,” the former mayor told the newspaper. “This isn’t racism. This is socialism or possibly anti-colonialism.”