Mayor Bill de Blasio’s approval rating took a 10-point hit since May, but he continues to hold a sizable lead over GOP mayoral candidate Nicole Malliotakis, according to a poll released Monday.

Fifty percent of voters polled had a favorable opinion of de Blasio, compared to 42 percent who had an unfavorable view of the mayor, according to the Quinnipiac Poll. In May, de Blasio had a 60 percent approval rating, and 34 percent disapproval rating.

De Blasio’s polling decline comes as he and Gov. Andrew M. Cuomo continue to publicly feud over who should shoulder the cost of repairing the city’s aging subway system.

“Leave out the one big question — the re-election matchup — and this is a pretty bad poll for Mayor Bill de Blasio,” said Maurice Carroll, assistant director of the Quinnipiac University poll, adding that “on the standard traits — leadership, empathy, and honesty — all the numbers are down.”

Asked about the dip in poll numbers, de Blasio’s campaign spokesman Dan Levitan, said “polls go up and polls go down.”

“Our campaign is about the mayor’s record and vision for the future, and we are going to remind New Yorkers that under Bill de Blasio, crime is at record lows, graduation rates and test scores are at record highs, and under this Mayor tenants have been protected,” Levitan said.

De Blasio leads Malliotakis, a Republican state assemblywoman from Staten Island, 57-22 percent, according to the poll. Despite the 35-point gap between the two major party candidates, voters were split — 46-46 percent — when asked if de Blasio deserved to be re-elected in the fall.

Malliotakis, who emerged as the GOP’s presumptive nominee in June after businessman Paul Massey dropped out of the race and independent candidate Bo Dietl failed to win a legal bid to run on the Republican line, continues to struggle with name recognition, according to the poll.

Seventy-eight percent of voters polled said they don’t know enough about Malliotakis to form an opinion on her candidacy.

Malliotakis’ campaign spokesman Rob Ryan, in a statement, said the results indicated a growing number of voters “don’t like” the mayor’s handling of local issues, and those voters would come to learn more about Malliotakis in the coming months.

“As we grow closer to Election Day, New Yorkers will realize that this is a race between Mayor ‘I don’t care’ de Blasio on the Democratic line and Assemblywoman Nicole Malliotakis on the Republican line,” Ryan said.