The last time “American Idol” endured ratings so low, Brian Dunkleman was the co-host, George W. Bush was president, and Simon Cowell was just some jerk from Britain.

But on Tuesday, with the show’s contestant field whittled to five, “Idol” dropped to its lowest overall audience since August 27, 2002, its first season on the air.

The Fox reality competition show was watched by an average of only 17.1 million viewers, according to Nielsen Fast Nationals, and was actually beaten in that benchmark by ABC’s “Dancing With the Stars” (averaged 19.6 million watchers).

Fox officials were quick to point out that “Idol” won the night in terms of the all-important adults 18-49 demographic, scoring a 6.0 rating/18 share, beating next closest competitor “Dancing” by a margin of 94 percent in that metric.

But the erosion of “Idol” this season, which has struggled amid the departure of longtime host Paula Abdul and the pending exit of Cowell, is undeniable, with the show dropping 13 percent from last week’s episode.

And that’s not a good thing, considering that April 17 broadcast was off 17 percent from the comparable week in 2009.