The by-election, caused by the resignation of Labour MP Dr Ian Gibson, was won with a majority of more than 7,000 by Chloe Smith.
But boundary changes have taken key Conservative areas into the new Broadland constituency.
It is now notionally Labour with the Tories needing an 8.3% swing to win it.
Tory candidate Ms Smith won with 13,591 - more than twice as many votes as Labour's Chris Ostrowski.
There was a swing from Labour to the Tories of 16.5% on a turnout of 46%.
The contest was triggered by Dr Gibson quitting after he was barred from standing again for the party over his expenses - sparking anger among some constituents.
Conservatives will be targeting Great Yarmouth, where the party needs a 3.7% swing to take the seat from Labour MP Tony Wright who had a 3,055 majority at the last election.
The Lib Dems are targeting Norwich South where they hope to unseat Labour MP and former Home Secretary Charles Clarke.
Lib Dem candidate Simon Wright needs a 3.7% swing to take the seat, represented by Mr Clarke since May 1997.
But the seat is also being targeted by the Green Party which has done well in local elections and is the second biggest party on Norwich City Council.
The Green Party candidate Adrian Ramsay is the national party's deputy leader.
The Conservative Party's Antony Little is also hoping to take the seat.
Boundary changes have also seen the creation of the new seat of Broadland.
Mainly formed from the old Mid Norfolk seat, the constituency is drawn from the Broadland District Council area but also includes six wards from the Norfolk North constituency, held by Lib Dem MP Norman Lamb.
Keith Simpson, the Conservative MP for North Norfolk, has followed the majority of his old constituency into the new seat - which has a notional Tory majority of 10.6%.
Other candidates of note in Norfolk include Elizabeth Truss, the Conservative candidate for South West Norfolk.
The former deputy director of think tank Reform fought off a challenge by some Conservative Party members, dubbed the "Turnip Taliban", after they found out about an affair she had previously with Mark Field MP.
Candidates so far announced include:
• Broadland: Conservative: Keith Simpson; Labour: Allyson Barron; Lib Dem: Daniel Roper; Green: Susan Curran; UK Independence Party: Stuart Agnew; BNP: Edith Crowther
• Great Yarmouth: Conservative: Brandon Lewis; Labour: Tony Wright; Lib Dem: Simon Partridge; Green: Laura Biggart; UK Independence Party: Alan Baugh; BNP: Bosco Tann
• Mid Norfolk: Conservative: George Freeman; Labour: Elizabeth Hughes; Green: Timothy Birt; BNP: Christine Kelly; UK Independence Party: Richard Coke
• North Norfolk: Conservative: Trevor Ivory; Labour: Phillip Alan Harris; Lib Dem: Norman Lamb; Green: Andrew Boswell; UK Independence Party: Michael Baker
• North West Norfolk: Conservative: Henry Bellingham; Labour: Manish Sood; Lib Dem: William Summers; Green: Michael de Whalley; BNP: David Fleming
• Norwich North: Conservative: Chloe Smith; Labour: John Cook; Green: Jessica Goldfinch; BNP: Thomas Richardson; UK Independence Party: Glenn Tingle; Independent: Bill Holden
• Norwich South: Conservative: Antony Little; Labour: Charles Clarke; Lib Dem: Simon Wright; Green: Adrian Ramsay; UK Independence Party: Stephen Emmens; BNP: Len Heather
• South Norfolk: Conservative: Richard Bacon; Labour: Mick Castle; Lib Dem: Jacqueline Howe; Green: Jo Willcott; UK Independence Party: Evan Heasley; BNP: Helen Mitchell
• South West Norfolk: Conservative: Elizabeth Truss; Labour: Peter Smith; UK Independence Party: Delia Hall; BNP: Dennis Pearce