Take no chances. Make no mistakes. Maintain strict message discipline. Like a football team two up with 20 minutes to play, the Conservatives think the only way they can lose the election is if they throw it away.

The contrast between the manifesto launched by Boris Johnson and Labour’s last week was marked. Behind in the polls and with only three weeks to go before election day, Jeremy Corbyn has gambled that voters are ready for radicalism. In sporting terms, he has thrown on three strikers as subs and sent his centre half up from the back in the hope of getting back in the game.

The prime minister, by contrast, is seeking to run down the clock until 12 December, relying on the fact that his “get Brexit done” line has cut through. Things started to go pear-shaped for Theresa May in 2017 when her manifesto plans for social care were dubbed a “dementia tax”. This time, the Conservatives have said the answer is to build a long-term, cross-party consensus.

Johnson’s pitch throughout the campaign has been that Britain’s departure from the EU will unleash a wave of pent-up investment and, by ending the uncertainty, lead to faster economic growth.

But there is no guarantee that this will happen, particularly since even if Brexit does go ahead on 31 January next year, the rest of 2020 will be spent trying to conclude a trade deal with the EU before the transition period ends. The forecasts for growth and borrowing that will be provided by the independent Office for Budget Responsibility for the budget that will take place once the election is over will not make pretty reading.

So while Johnson was upbeat at the manifesto launch, the document itself was a much more cautious affair. While a Labour government would be spending £83bn a year more on day-to-day spending by the end of the next parliament, the Conservatives would limit themselves to a £3bn a year increase. The two parties are also a long way apart on capital spending: both would borrow to invest but Labour would be prepared to borrow an addition £80bn each year, the Conservatives £3bn next year rising to £8bn by 2023.

One reason for that is that most of the spending increases announced in the manifesto were announced by the prime minister shortly after he arrived in Downing Street and were included in September’s spending round. There is more money for the NHS but as Paul Johnson, the director of the Institute for Fiscal Studies noted, only a big rise when compared to the tight settlements of the past decade. Over a longer period, the past 40-50 years, it will be a smaller than average increase.

The safety first approach has its risks. Pledging to spend more on hospitals, schools and the police has been a recognition that voters have wearied of austerity and want a change of course. This is an election that is being fought on ground that suits Labour.

To counter that disadvantage, Johnson has offered modest increases in spending in areas that focus groups have suggested are politically sensitive: such as the time it takes to get a GP appointment and the poor state of Britain’s roads. He has shelved plans to raise the threshold at which the 40% income tax bracket kicks in, choosing instead to raise gradually the level at which national insurance contributions are levied. In addition, he has promised a triple tax lock: no increases in income tax, NICs or VAT rates over the next parliament. “Brexit is happening”, said Torsten Bell, director of the Resolution Foundation think tank, “but big tax cuts aren’t.”

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While Corbyn said the manifesto was a package for billionaires, the Conservatives hope it will go down well with the electorate, especially former Labour voters in the Midlands and the North of England. Johnson thinks the public remains suspicious of parties making big spending commitments that rely on substantial extra borrowing.

After saying Labour’s manifesto lacked credibility, the IFS’s Johnson said the Conservative offering was notable for its lack of ambition. “If a single Budget had contained all these tax and spending proposals we would have been calling it modest. As a blueprint for five years in government the lack of significant policy action is remarkable.”

This is a risk because teams that are two up with 15 minutes to go and play it safe sometimes lose. Not often, but often enough for Johnson to keep glancing at the clock.