It was a tight race earlier this summer for top demo honors on Wednesday nights, but CBS’ ”Big Brother” has emerged the clear leader over NBC’s ”America’s Got Talent.” Last night, ”Brother” matched its season high and paced the Eye to victory in key demos, while ”Talent” and NBC both led the way in total viewers.

According to preliminary nationals from Nielsen, ”Big Brother” dominated the night’s opening hour with a 3.2 rating/10 share in adults 18-49 and 8.2 million viewers overall , up about 10% week to week and matching its top demo delivery of the summer. The Eye then fell off from there with encores of ”Criminal Minds” (1.5/4 in 18-49, 5.3 million viewers overall) and ”CSI” (1.2/3 in 18-49, 5.8 million viewers overall). CBS won the night in adults 18-49 and 25-54.

At NBC, gameshow ”Minute to Win It” (1.4/4 in 18-49, 5.4 million viewers overall) was followed by ”America’s Got Talent” (2.5/7 in 18-49, 10.3 million viewers overall), which was on the low side but still led its hour in all categories and was the night’s most-watched program overall. And at 10, a repeat of ”Law and Order: Special Victims Unit” (1.4/4 in 18-49, 5.1 million viewers overall) finished just a tick out of the 18-49 lead.

Univision moved up to third place on the night in 18-49 and claimed the night’s top scripted show in the demo, ”La Fuerza del Destino” (2.0/5 in 18-49, 4.3 million viewers overall).

ABC was on the high side, grabbing its best repeat comedy numbers of the summer with an hour of ”The Middle” (1.1/4 in 18-49, 4.3 million viewers overall at 8 and 1.3/4 in 18-49, 4.1 million viewers overall at 8:30) and ”Modern Family” (1.2/3 in 18-49, 5.8 million viewers overall). And hitting a series high at 10 p.m. , and winning its slot in 18-49 , was newsmag ”Primetime: Nightline” (1.5/4 in 18-49, 4.3 million viewers overall).

Fox lagged well behind its rivals with new alternative series ”Buried Treasure” (1.0/3 in 18-49, 3.3 million viewers overall), which was followed at 9 p.m. by a repeat of last week’s episode (1.0/3 in 18-49, 3.2 million viewers overall).

Preliminary 18-49 averages for the night: CBS, 2.0/6; NBC, 1.7/5; Univision, 1.6/5; ABC, 1.5/4; Fox, 1.0/3; CW, 0.4/1.

In total viewers: NBC, 6.9 million; CBS, 6.4 million; ABC, 4.4 million; Univision, 3.7 million; Fox, 3.2 million; CW, 1.0 million.