The Middlesbrough singer, who is mentored by Nicole Scherzinger, has so far collected 52% of the popular vote.
Jahmene Douglas has 30%, while Christopher Maloney is trailing in third place with 18%. A total of 9,000 people have already voted in the poll.
Digital Spy readers correctly tipped Little Mix to win last year's series. However, in recent weeks Maloney has remained fixed to the bottom of DS's weekly 'Who Sang Best' polls and has survived without once appearing in the bottom two.
Arthur has previously appeared in a sing-off, alongside Ella Henderson.
The 24-year-old, who performed a homecoming gig at Middlesbrough Town Hall with Scherzinger earlier this week, is joint favourite with the bookmakers to be crowned the champion on Sunday evening. Both Arthur and Douglas have odds of 5/4 with Paddy Power.
Maloney is backed at the slightly longer odds of 7/2.