Harris has competed in all three rounds of the series and was in exceptional form at King’s Lynn earlier this month, dropping just one point in five rides.
He was joined by Michael Palm Toft in the home round and then Hans Andersen at Ipswich and King’s Lynn, so Nicholls will make his debut in the event on Monday.
Harris’s super solo display and a battling third place from reserve Jordan Jenkins helped Panthers to climb the rankings at the Adrian Flux Arena, moving ahead of Wolverhampton.
Their record in the competition so far shows an upturn each round with finishes of sixth, fifth and fourth so far.
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Ipswich, Sheffield and King’s Lynn seem set to fight it out for overall honours as they have a healthy advantage over the remaining clubs at the halfway stage and are covered by just four points.
Start-time at Monmore Green on Monday has been pushed back to 8pm in view of the forecast of extreme temperatures.
The meeting is available to watch via the British Speedway Network, with full details available at https://watch.britishspeedway.co.uk.
PREMIERSHIP PAIRS ROUND 4 LINE-UP:
BELLE VUE: Max Fricke, Brady Kurtz, Tom Brennan (RS).
IPSWICH: Jason Doyle, Troy Batchelor, Danyon Hume (RS).
KING’S LYNN: Josh Pickering, Richard Lawson, Jason Edwards (RS).
PETERBOROUGH: Chris Harris, Scott Nicholls, Jordan Jenkins (RS).
SHEFFIELD: Adam Ellis, Tobiasz Musielak, Connor Mountain (RS).
WOLVERHAMPTON: Sam Masters, Nick Morris, Joe Thompson (RS).