By Heath Pickering. Deputy Editor, Election Watch

The federal election will be held on the 2 July. There are 150 lower house seats up for grabs. Many will be tight contests. Here are five key battles:

1. New England - Barnaby Joyce v Tony Windsor

Nationals leader and Deputy Prime Minister Barnaby Joyce currently holds the seat of New England in the NSW Northern Tablelands by a two-party preferred margin of 70%.

His challenger, Independent Tony Windsor, previously held the seat from 2001 until his retirement in 2013. A recent poll suggested that Tony Windsor could potentially win on preferences if an election was called soon.

Windsor famously held the balance of power, along with other independents, in 2010 and chose to support the Labor government led by Prime Minister Julia Gillard. If Barnaby Joyce were to lose, Turnbull would have to nominate another Deputy Prime Minister—most likely another Nationals MP. The current Deputy Leader of the Nationals is Fiona Nash.

Despite this, Barnaby Joyce has led a safe campaign. The Federal Government recently delayed a controversial 'backpacker tax' that would have affected farmers' ability to recruit from a vital labour market. Plus, Mr Joyce has also led a review into the decreasing price of milk that has hurt dairy farmers across Australia.

Australian Electoral Commission profile of the seat of New England

2. Indi - Cathy McGowan v Sophie Mirabella

Independent Cathy McGowan holds the seat of Indi in north east Victoria by a tiny margin of less than 500 votes. In one of the stunning upsets at the 2013 election, she beat Liberal sitting member, Sophie Mirabella, who held the seat with a ‘safe’ 9% margin. Not only was Mirabella expected to retain her seat, but she was also guaranteed a Cabinet position in the Government of former Prime Minister Tony Abbott.

Part of the loss was attributed to a strong grassroots campaign from Cathy McGowan. Mirabella won the Liberal pre-selection last year and is trying to reclaim her old seat at the next federal election.

However, her campaign has started poorly. She recently told a Sky News forum she had secured a $10 million dollar commitment for Wangaratta hospital, which was subsequently withdrawn after she lost her seat to Independent Cathy McGowan. More recently, Nationals leader Barnaby Joyce said the best chance the Coalition have of regaining the seat was through the Nationals candidate Marty Corboy.

Australian Electoral Commission profile of the seat of Indi

3. Eden-Monaro - Peter Hendy v Mike Kelly

The so-called ‘bellwether’ seat has always gone to the government of the day since 1972. As the table above shows, the seat has swung six times in the last 44 years. Current sitting member Liberal Peter Hendy holds a narrow 1-2% margin. His challenger will be the Labor Party’s Mike Kelly. Kelly held the seat from 2007-2013 and narrowly lost by around 1,000 votes at the 2013 election.

Peter Hendy's campaign has suffered an early blow. A leaked email from the Menzies Group, an informal gathering of Liberal Party members, urged conservative supporters to 'boycott' Hendy's campaign because of his role in ousting former Prime Minister Tony Abbott.

Recent boundary changes to the seat of Eden-Monaro could tilt the seat further in favour of the Coalition. The new map casts a wider distribution to rural areas such as Yass and Tumut, while excluding coastal areas Batemans Bay and Moruya.

Australian Electoral Commission profile of the seat of Eden-Monaro

4. Brisbane - Trevor Evans v Pat O'Neill

With the surprise retirement of Theresa Gambaro, the seat of Brisbane has become a hot contest. Gambaro has held the seat since 2010, but only with a narrow margin of 1-3%. Labor previously held the seat between 1980-2010. The slightest of swings away from the Liberal National Party is likely to hand control back to Labor.

Openly gay former Army Major, Pat O’Neill, has been pre-selected by the Labor party for the seat. He will be competing against LNP candidate Trevor Evans, a former CEO of the National Retailer Association and another openly gay candidate. This will be the first time two openly-gay candidates from both major parties have campaigned in the same electorate.

The LNP candidate has already faced criticism over his website. BuzzFeed recently reported that Trevor Evans had copy and pasted his 'personal' profile from a fake US Congressman, set up by a digital design agency.

Australian Electoral Commission profile of the seat of Brisbane

5. Melbourne - Adam Bandt v Sophie Ismail

Labor held the seat of Melbourne for over 100 years before the Greens won the seat in 2010—the party’s only seat in the House of Representatives. Adam Bandt successfully re-won the seat in 2013 despite Liberal Party preferences flowing to Labor in an attempt to oust the Greens member. Bandt holds the seat with a 6% margin.

His challenger is Labor’s Sophie Ismail, who comes from a migrant family, is openly gay and is a human rights and employment lawyer. At the start of the campaign she contradicted Labor party policy on asylum seekers by saying that she has "concerns about turn-backs". Under Labor policy, boats carrying asylum seekers will be turned back if safe to do so, and at the discretion of the Labor Government. Her comments, and similar comments from several of her Labor colleagues, have enabled the Liberal Party to post advertisements criticising Labor's ability to remain strong on border security.

Australian Electoral Commission profile of the seat of Melbourne

Note: This article will be continuously updated during the election campaign. We were originally following Clive Palmer's seat of Fairfax until he announced that he would not recontest his Sunshine Coast seat.

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Banner image: Flickr/paolaharvey