Newark Mayor Cory Booker’s commanding Democratic primary lead in the New Jersey Senate special election is holding strong.

The latest Quinnpiac University Poll, released Tuesday, found Booker far ahead of the competition. He led with 52 percent, followed by Rep. Frank Pallone Jr. with 10 percent, Rep. Rush D. Holt with 8 percent and state Speaker Sheila Oliver with 3 percent.

With the race half over, the numbers highlight how difficult it will be for Booker’s opponents to move the needle. The institute’s previous poll, released June 10, showed almost identical results.

“Political observers wondered why Congressmen Frank Pallone and Rush Holt didn’t make a deal for one of them to step out and throw his support to the other,” Quinnipiac Polling Director Maurice Carroll said. “These results show that probably wouldn’t help. Pallone’s and Rush’s combined total in the Democratic primary still trails Booker’s tally almost 3-1.”

The four Democrats are vying for the chance to replace the late Sen. Frank R. Lautenberg, D-N.J. The primary will be held Aug. 13, and the special election will take place Oct. 16.

The Democratic primary winner will be heavily favored over likely Republican nominee Steve Lonegan, a conservative activist. However, Booker was the only Democrat to lead Lonegan in a hypothetical special-election matchup by a statistically significant margin. The other Democrats remain largely unknown and finished close with Lonegan head-to-head.

The survey of 1,068 registered voters was conducted July 2-7 and had a 3-point margin of error. The survey included 400 Democrats with a 4.9-point margin of error.