“American Idol” is sprinting to the finish line, racking up hefty year-to-year gains Wednesday night and lifting Fox into a near tie for the May sweep demo lead.

As the third week of the ratings period came to a close, “Idol” and the season finales of “That ’70s Show” and “Stacked” put Fox in the winner’s circle once again. Night also saw ABC’s “Lost” picking up more steam as well as strong season-enders for UPN’s “America’s Next Top Model” and the WB’s “Smallville.”

From 9 to 9:30, the six broadcast nets combined for a 63 share in adults 18-49 — their highest for any half-hour so far this sweep. They figure to top that next Wednesday, though, when the finales of “American Idol” and “Lost” go head-to-head from 8 to 10.

Meanwhile, with the “Idol,” “House” and “24” finales still ahead for Fox and many of the big CBS guns already fired off, Fox is expected to win the month in 18-49. Through three weeks, though, the Eye still edges Fox (4.3 rating/12 share to 4.2/12), and CBS is projected to win comfortably for the month in adults 25-54 and total viewers.

According to Nielsen nationals for Wednesday, Fox’s “American Idol” (11.8 rating/29 share in adults 18-49, 27.93 million viewers overall) towered over the competish and was way up over the same night a year ago (9.8/23, 22.4 million). Also for the net, “Stacked” led at 9:30 (5.2/13 in 18-49, 11.57m) and the hourlong season finale of “That ’70s Show” placed second at 8 (4.2/12 in 18-49, 8.77m).

Wednesday runner-up ABC led easily at 8 with “Lost” (6.7/19 in 18-49, 18.62m), which hit 11-week highs, but then dropped off from 9 to 11 with a two-hour “Alias” (3.5/9 in 18-49, 8.86m), which went up against mostly season finales on the other nets.

CBS was paced by a slot-leading victory at 10 for “CSI: NY” (4.5/12 in 18-49, 12.30m) over NBC’s “Law & Order” (4.0/10 in 18-49, 12.41m), with the latter wrapping the May sweep down 38% vs. last year. Also for the Peacock, there was no pop for the finale of limited-run drama “Revelations” (3.0/8 in 18-49, 8.15m).

UPN’s “America’s Next Top Model 4” (3.0/9 in 18-49, 6.08m) ended its season with potent numbers, placing third at 8 in 18-34 (3.0/9) and second in women 18-34 (5.4/16) — setting a network timeslot record in the latter. “Model 4” ended its run up in most categories over “Model 3.”

The WB’s 90-minute season finale of “Smallville” was solid (2.5/7 in 18-49, 5.47m) despite opposing “Lost” and “Idol.”