FOX News Channel crushed its competition on the first night of the Republican National Convention, pointing to a growing partisan division among cable news viewers.

An estimated 3.9 million viewers watched the GOP's gathering on Fox in prime time on Monday, almost twice the audience for its two rivals — CNN and MSNBC — combined, according to Nielsen Media Research (search).

On a night that ABC, CBS and NBC didn't cover the convention live, CNN had 1.3 million viewers and MSNBC had 854,000, Nielsen said.

It was a lot different a month ago in Boston. During the one night that the three big broadcasters didn't cover the Democratic convention live, CNN had 2.9 million viewers, MSNBC had 1.854 million and FOX had 1.845 million, Nielsen said.

The Democratic convention numbers released by Nielsen measured viewership from 10 p.m. to 11 p.m. For the Republican convention, it was 8 p.m. to 11:30 p.m.

The results are consistent with a poll released earlier this year that found Republicans prefer to get their news from FOX News Channel while Democrats like CNN.

The differences from 2000 are striking. Fox News Channel had 676,000 viewers for the first night of the GOP convention back then, a little more than half of CNN's audience. FOX has sharply increased its distribution since then.

PBS, which also telecast more than three hours of convention coverage on Monday, was seen by 1.9 million viewers, Nielsen said.