The track was first released back in 2015 as part of the star’s My Everything album, but has risen to prominence again after a suicide bomber targeted her show at Manchester Arena last month, leaving 22 dead.
With One Last Time being the show’s encore that night, finishing just moments before the deadly blast, it became a tribute song to those who lost their lives.
It flew back up the charts in the aftermath of the tragedy, hitting Number 11, but could go all the way this week.
The progress comes after the fundraising One Love Manchester benefit gig, which Grande co-produced.
The UK singles chart tracks sales and streams from 0:00 on a Friday to 23:59 on a Thursday; and at this mid-way stage, One Last Time is currently No2, according to the Official Charts Company.
However, with the momentum sky-high after the show on Sunday, it is a very real possibility that it will overtake its closest competition – Despacito by Luis Fonsi and Daddy Yankee featuring Justin Bieber – by the end of the week.
Indeed, on iTunes – which measures sales via its own online store over a rolling 24-hour period – the dance-pop song is still at the summit.
The original album version is at No4, and another release of it is at No36. The overall official charts will merge all three ‘releases’ into one, increasing its chances of success even more.
76p from each 99p download will go directly to the We Love Manchester Emergency Fund in coordination with the British Red Cross and Manchester City Council. Over £10 million has already been raised.
Emotional Grande was joined by Katy Perry, Liam Gallagher, Coldplay, Miley Cyrus, Black Eyed Peas, Niall Horan, Little Mix and more at the show on Sunday.
One Last Time is out now.