In a matter of hours, American Pharoah could gallop into the record books as the 12th Triple Crown winner in horse racing history. But in the buildup to the Belmont Stakes, the betting public has swayed back and forth at the Pioneer of the Nile colt’s chances of ending the 37-year drought.

The three-year-old bay colt takes on the 1 1/2-mile dirt track early Saturday evening as a 1/2 odds favorite from the No. 5 post in the latest official odds from Elmont, New York.

The Kentucky Derby and Preakness Stakes winner’s betting line shifted throughout the morning and early afternoon from a morning line of 3/5, down to 1/5 and 2/5, and now 1/2.

As of time of publication, more than $4 million in bets have been placed on the Belmont. More than half, or $2.1 million, is riding on American Pharoah.

Among seven other contenders vying to upend the hopes of owner Zayat Stable and trainer Bob Baffert, Frosted holds steady with the best chance of denying American Pharoah at 5/1.

Given his fourth place finish at the Derby, and the five weeks of rest he’s accumulated by skipping the Preakness, Frosted serves as the toughest challenger to American Pharoah and will bolt out of the No. 6 gate.

But even Frosted’s odds have changed throughout the day. He opened at 5/1 morning line odds, and online odds makers listed him at the same or at 6/1. But at one point Saturday Frosted went to 7/1.

Materiality opened at 6/1, and he’s largely held pat since it was learned that trainer Todd Pletcher would point him at the Belmont. Like Frosted, Materiality is one of four contenders who lost to American Pharoah at the Derby and rested up in an attempt to thwart his Triple Crown hopes. He's currently at 7/1, but odds are changing as more bets are placed right up until the start.

The biggest long shot in the field remains Frammento at 20-1. The Midshipman colt wound up 11th at the Derby, and he hasn’t won a race since October at a 1 1/16-mile distance. Though he’s faced this year’s stakes field several times, including a fourth-place run at  the Grade 1 Blue Grass Stakes.

Weather doesn’t figure to be a factor unlike the Preakness, when torrential rains soaked the track roughly half an hour before the race. The forecast originally called for clear skies and a temperature of 70-degrees Fahrenheit when the race begins, but the latest readings from indicate a negligible dip to 69-degrees and most cloudy.

Actual Start Time: The approximate post time is 6:50 p.m. ET, so the Belmont will begin a few minutes after that once every horse has entered their starting gate.

Posts and Latest odds

1. Mubtaajihi 15/1

2. Tale of Verve 19/1

3. Madefromlucky 14/1

4. Frammento 20/1

5. American Pharoah 3/5

6. Frosted 5/1

7. Keen Ice 15/1

8. Materiality 7/1