WASHINGTON (CNN) Joe Biden has expanded his edge over the Democratic field in a new CNN poll conducted by SSRS, with 29% of Democratic and Democratic-leaning registered voters saying they back the former vice president.

That’s up 7 points compared with a late June CNN survey. No other candidate has made meaningful gains over that time.

The shift returns Biden to a double-digit lead over his nearest competitors, Vermont Sen. Bernie Sanders at 15% and Massachusetts Sen. Elizabeth Warren at 14%. Their support is largely unchanged since earlier this summer.

Aside from Biden’s increase, the only statistically meaningful change in the candidate standings is a 12-point decline in support for California Sen. Kamala Harris, who stood at 17% support in the June poll but now has the backing of 5% of potential Democratic voters. That’s similar to the level of support she had in the spring before a surge following her initial debate performance.

The June CNN poll was conducted in the days immediately following the first round of Democratic National Committee-sanctioned debates among the presidential candidates. Biden’s performance in that debate was widely panned, while Harris had a standout moment challenging him over his views on school busing integration. Biden’s numbers have rebounded since then in other polling as well, and Harris’s have returned to roughly where they were pre-debate.