Two weeks down. Four weeks to go. The General Election campaign is now in full swing. So far the polls have shown the Conservatives comfortably ahead, with consistent leads over Labour in every opinion poll since the election was called.

Of course, we all recall this was the same situation at this stage of the 2017 election. Moreover, the nature of the first past the post electoral system means that opinion polls based on crude percentage share of the vote are often little help in projecting the likely distribution of seats.

Although Boris Johnson is keen to frame the election as a straight choice between himself and Jeremy Corbyn, it is really a series of local contests. It also remains to be seen how tactical voting based on Brexit preferences will impact this election, especially as the anticipated realignment based on ‘leave’ or ‘remain’ didn’t materialise in the last election.

Here are  six factors which will determine the outcome of the election.

1.  A Liberal Democrat resurgence
The Liberal Democrats have seen their fortunes transformed in the past two years, coming second in the European Parliament elections in May and polling around 14-15%, compared to the 7% they scored in 2015 and 2017. Their activist base is motivated, some well known Conservative figures have come out in support of them, and they have thrown resources at parts of the country which voted ‘remain’ in the EU referendum.

This should help them increase their representation in areas like the South East and South West, where they are the main challengers to the Conservatives.

However, the electoral system disadvantages the Liberal Democrats and it is possible that a big increase in their vote share will translate into a disappointing number of seats, particularly given the high expectations set by Jo Swinson.

There is also the likelihood that in constituencies where Labour is the main opposition to the Conservatives, any increase in the Lib Dem vote will come at the expense of Labour, helping the Tories hold on to seats they might otherwise have lost.

2. The impact of the Brexit Party
The decision by Nigel Farage to stand down Brexit Party candidates in 317 constituencies won by the Conservatives in 2017 will boost Boris Johnson’s hopes of holding onto those seats.

The fall in support for the Brexit Party’s polling, from 30% at the European elections in May to under 7% also suggests that Farage will play less of a role in the outcome of this contest than might have been expected.

It is still not clear what impact the Brexit Party will have in Labour constituencies which the Tories need to win if they are to secure a majority. In 2017 the Conservatives hoped that UKIP would act as a “gateway drug”, whereby former Labour voters who had switched to the eurosceptic party would then transfer their support to the Tories. However, tribal voting behaviour is strong and Labour went on to comfortably hold seats which had previously seen strong results for UKIP.

While in most Labour constituencies the presence of a Brexit Party candidate should disadvantage the Conservatives, this will not be the case everywhere and in some seats their intervention may cause some unexpected results.

3. Boris vs Corbyn
If the Conservatives’ strategy is to succeed, they need a good showing against Labour in the North and the Midlands, where most of their target constituencies are only winnable by either of the two main parties.

With Jeremy Corbyn’s favourability ratings far lower than those of the Prime Minister, this should be achievable. However, while the Prime Minister is charismatic and a strong campaigner, he also has a tendency to go off script. There is also the danger of further revelations about Boris’s colourful private life, which could derail the Conservative message.

Although Corbyn had a slow start in 2017, as the weeks went on he was able to present himself as a more passionate and accessible politician than most commentators considered possible. A series of televised one on one debates between the two party leaders this time creates the opportunity for Corbyn to reset voters’ perceptions of him as a potential Prime Minister.

The Conservatives are also in danger of repeating the mistake of attacking Corbyn on issues such as his views on Venezuela or the Middle East, which excite their activists but don’t resonate with the public.

4. What happens in Scotland and Wales
The SNP continue to dominate electoral politics in Scotland. With Ruth Davidson standing down as the Scottish Conservatives’ leader, the 13 seats won by the Tories in 2017 are at risk.

The realignment of Scottish politics, however, is not yet complete, with some polls showing Labour sliding into fourth place north of the border. While the SNP will remain the largest party in Scotland by a wide margin, the way in which the seats they don’t win are divided between the Tories, Labour and the Liberal Democrats will impact on the parliamentary arithmetic.

In Wales the situation is happier for the Conservatives, and they may gain seats here.

5. Manifesto woes
In 2017 a series of botched manifesto commitments on adult social care and fox hunting was hugely damaging for the Tory campaign.

Labour have been effective at branding innocuous or poorly understood Conservative policies as “nasty” and distilling complex policy issues into easily understood attack lines. Their messaging around the risk to the NHS from a trade agreement with the United States, while based on a false premise, has found public sympathy.

In 2017, Labour seized the initiative with a series of left-wing policies that appealed to carefully targeted sections of the electorate. The danger this time is that they over-reach with proposals such as a four day working week, which are perceived as impractical or undeliverable.

Having learnt a painful lesson two years ago, the Conservative manifesto will likely be a short document that gives little away in terms of policy detail.

6. Tactical voting
Every election sees attempts to coordinate the anti-Conservative vote through tactical voting arrangements. This time there are efforts through the People’s Vote campaign and websites like Remain United to encourage people to vote for candidates who are likely to support a second EU referendum.

The Liberal Democrats have also stood down in some seats being contested by former Conservative MPs who share their views on Brexit, such as Beaconsfield, where they are giving Dominic Grieve a clear run.

The effectiveness of these efforts remains to be seen. Such campaigns excite Westminster insiders but have little reach amongst the public as a whole, while independent candidates normally have limited success in UK elections except in very local circumstances. This time could be different.