Josh Haner/The New York Times

More people watched former President Bill Clinton’s speech to the Democratic National Convention on Wednesday night than tuned in to see the N.F.L. season opener.

But the game appeared to cut into the convention’s ratings, which were lower than Tuesday night’s.

According to preliminary ratings from Nielsen, 20.6 million watched the convention from 10 p.m. to 11 p.m., while 20.1 million people watched the New York Giants-Dallas Cowboys game during the same hour.

Both events had fewer viewers in that hour than Michelle Obama’s speech on Tuesday, the first night of the convention. About 26.2 million people tuned in to hear the first lady, Nielsen reported.

Mrs. Obama was also a bigger draw than Ann Romney, the wife of Mitt Romney, the Republican presidential nominee, whose speech last week at the Republican convention attracted 22.3 million viewers.

From 10 p.m. to 11 p.m., ABC was the most-watched network, with 4.59 million viewers. CBS had 4.41 million; MSNBC had 4.39 million; CNN had 4.13 million; and Fox News drew 3.1 million.

In a telling sign of who is tuning in more – liberals or conservatives – MSNBC beat Fox News in the ratings for the second night in a row. Yet last week during the Republican National Convention, Fox News had higher ratings than anyone, including the traditional broadcast networks.

So far, interest in the Democratic National Convention is on par with 2008, when the first and second nights were seen by 22.3 million and 26 million people, respectively.