The McCain campaign scoffed at the ad, which featured clips from Obama speeches, vignettes of swing-state voters facing hard times and testimonials from elected officials, business leaders and military experts. “As anyone who has bought anything from an infomercial knows, the sales-job is always better than the product,” McCain spokesman Tucker Bounds said in a statement. “Buyer beware.”

Here’s the first 27 minutes of the Obama ad, minus the conclusion, which was broadcast live from an Obama rally in Sunrise, Fla.:

A Nielsen release detailed the preliminary ratings:

• Overall, for the six networks that aired the program simultaneously, the spot had a household rating of 21.7 percent (meaning that 21.7 percent of all households watching television were tuned to the spot.)

• By comparison, the final debate between the two presidential candidates received a 38.3 household rating in the top 56 local TV markets. The candidates’ first debate 9/26 received a 34.7 household rating in the top 55 markets; their second debate 10/7 received a 42.0 household rating in those markets.

• The last presidential candidate to air a paid simulcast was Ross Perot in 1996, which received a national household rating of 16.8.

• Last night, the Baltimore market had the largest TV audience, with a household rating of 31.3, while the Portland market had the lowest household rating: 14.2.

Denver ranked 32nd among 56 cities reflected in the overnight Nielsens, with 20.8 percent of televisions tuned to the Obama ad.

The ad garnered 26.3 million viewers on CBS, NBC and Fox, according to preliminary Nielsen ratings reported by The Hollywood Reporter (THR). It outperformed the usual network programming for a Wednesday night in that time slot, THR said.

ABC’s “Pushing Daisies,” the only major network show airing against the Obama ad, improved its ratings by 16 percent but still lost the ratings competition, coming in fourth place with 6.8 million viewers and a 2.2 share. By comparison, NBC’s airing of the Obama ad had 9.8 million viewers, CBS had 8.6 million and Fox had 7.9 million, THR reported.

The ad aired live on CBS, NBC, FOX, UNIVISION, MSNBC, and NY1. BET aired the ad in different time periods so wasn’t counted in the overnight Nielsen ratings.

Last week, 38.4 million watched Obama accept his party’s nomination — including 7.5 million African Americans, more than twice as many as watched McCain’s address. Five million more white viewers watched the Republican than watched the Democrat. Obama’s audience blasted previous records for convention speeches.

TV critics speculate McCain benefitted from NBC’s broadcast of the first regular season NFL game between the New York Giants and Washington Redskins, which ended right before McCain’s speech started.

On Wednesday night, Alaska Gov. Sarah Palin drew nearly as many viewers as Obama in her first prime-time speech, with more than 37 million watching her accept the vice presidential nomination.

The Nielsen numbers don’t include PBS or C-Span viewers, or online audiences and households using digital video recorders. PBS estimates 2.7 million watched its coverage of the RNC Thursday, compared with 3.5 million Obama viewers. With those figures added in, Obama edged McCain slightly in the live audience contest.

On average, viewership of this year’s conventions is two- to three-times the audience for the parties’ 2004 gatherings. Nielsen measured viewers for McCain’s speech on ABC, CBS, NBC, CNN, Fox News Channel, MSNBC, Telemundo, and Univision. Two networks — BET and TV One — carried Obama’s speech but didn’t broadcast McCain’s.

The Nielsen overnight numbers didn’t count PBS or C-SPAN viewers, or those who watched the speech online. PBS estimated 3.5 million households watched its coverage of the Democrat’s historic speech. Figures for TIVo and other digital-recorder users won’t be available until next week.

Overall, the Democratic National Convention broke viewer records, with an average 22.5 million households tuning in during prime time over the four days. The previous record for a political convention was the 1976 Republican edition, which drew an average 20 million households, when the three major networks broadcast the convention every night. This year, the broadcast networks just showed the 8:00 p.m. to 9:00 p.m. hour.

Nielsen measured viewers for ABC, CBS, NBC, CNN, FOX News Channel, MSNBC, BET, TV One, Univision and Telemundo. With 8 million viewers, CNN won the hour during the Obama speech, the first time the network has ever scored more viewers than any other network.

The Obama ratings were higher than this year’s American Idol finale, the opening ceremonies for the 2008 Summer Olympics, and the 2008 Academy Awards.