The N.F.L. is under pressure from falling television ratings, lawsuits over its handling of concussions, and fan opposition to player protests during the national anthem.

Yet investors keep lining up to help start new football leagues. On Tuesday, the longtime N.F.L. executive Bill Polian and the television and movie producer Charlie Ebersol became the latest entrepreneurs to join the fray when they unveiled plans for the Alliance of American Football.

There have been several short-lived football leagues before, including the United Football League, United States Football League and XFL. Like others before them, Polian and Ebersol say they have a formula for success. They have acquired investments from Silicon Valley firms that will allow their eight-team league to start playing a week after the Super Bowl in February 2019. Their partners include CBS, which will show a few games on its main channel and some on its cable network. They will also launch a smartphone app on which fans will be able to stream games and play fantasy football.

The league will also aim for two-and-a-half hour games (N.F.L. games generally last at least three hours). To achieve that, there will be no kickoffs or extra points — only 2-point plays — and a 30-second play clock, as opposed to the N.F.L.’s 45-second clock. There will also be no television timeouts, which will lead to about 60 percent fewer commercials.