A new poll commissioned by a D.C.-based, pro-business advocacy group finds a tighter D.C. mayoral race than seen in previously published polling, with Democrat Muriel E. Bowser leading independent David A. Catania by eight percentage points among likely voters.

An NBC4/Washington Post/Marist poll conducted last month found a 17-point spread between those two candidates, with independent Carol Schwartz further behind. The poll done this week for Economic Growth D.C. found Catania with a similar level of support among likely voters — 27 percent versus 26 percent in the Post poll — but found lower levels of support for Bowser. The new poll puts Bowser’s support at 35 percent versus 43 percent in the Post poll; Schwartz is at 11 percent versus 16 percent previously.

“What this says to me is the race is closer than a lot of people think it is,” said Dave Oberting, Economic Growth D.C.’s executive director. “It makes the next five weeks pretty interesting.”

The live-caller Economic Growth D.C. CapitalDecision2014 poll reached 1,023 frequent D.C. voters, plus a random sample of new registrants, between Sept. 28 and Sept. 30. The results carry a margin of error of three percentage points. The survey did reach cellphone users, though a smaller proportion than that of cellphone-only households overall in the District, which could lead to undersampling of some groups.

Oberting said his group paid for the poll in its entirety and is not supporting any particular mayoral candidate: “We have not donated,” he said. “We have not intervened in any way, and we do not have plans to at this moment.”

The new poll differs from the NBC4/Washington Post/Marist poll in selecting respondents from a voter list rather than by dialing random numbers. The composition of the two polls’ samples is markedly different in some ways, including by race: In the Post poll, African Americans narrowly outnumbered whites, 48 to 43 percent. In the new survey, 53 percent of likely voters are white, while 42 percent are black and 5 percent Hispanic or Latino.

The smaller share of African Americans may have hurt Bowser in that poll, given she led by 55 to 11 percent among blacks in the Post survey, and Catania led by 41 to 30 percent among whites.

In other notable findings, the Economic Growth D.C. CapitalDecision2014 poll tested a hypothetical head-to-head matchup between Bowser and Catania, and found that Bowser’s lead would widen slightly — Bowser 43 percent, Catania 33 percent — were Schwartz not in the race, further evidence that Schwartz isn’t playing spoiler for either candidate.

Asked their impressions of each candidate, Bowser and Catania fared similarly — both has name recognition over 80 percent with favorable impressions outstripping unfavorable impressions by a roughly two-to-one margin.

Scott Clement contributed to this post.