One of the big four broadcast networks has established a huge early ratings lead for the May sweeps period while another one is struggling to stay in the top four.

Media Life reports that ABC is well out in front after winning four of the period’s first seven nights and averaging a 1.91 rating in the key 18-49 demo.

Week 1 of May sweeps wrapped Wednesday, April 29. Through that night, ABC is up 23% from a year ago in adults 18-49.

Trailing ABC are CBS in second place with a 1.34 and NBC close behind with a 1.32, followed by fourth-place Fox with a 1.03. All of the major nets chasing ABC are down from a year ago: CBS, down 18%; NBC, down 9%; and Fox, down 24%.

The report notes that Fox is barely ahead of fifth-place Univision, which has a 0.96 average rating, down 16% from last year.

One other broadcast network has posted gains over the year-ago period: The CW is up 4% with a 0.61 average.

ABC has benefited from a strong performance by “Grey’s Anatomy” along with a huge turnout for Diane Sawyer’s “20/20” interview with Bruce Jenner, which delivered a 5.2 average.