One hundred and seventeen years of history says Labor should win the seats of Longman and Braddon in today’s by-elections.

The fact that it might lose one or both is why Bill Shorten’s leadership is being questioned.

Because in 147 federal by-elections since 1901, a government has only won a seat from the Opposition once.

The circumstances of that 1920 victory were unique. It was the only time in history where a by-election was forced after an MP was expelled from Parliament – for treason.

The usual outcome in by-elections is a four percent swing to the Opposition, so the bar for Labor losing either of these seats is set pretty high.

The stakes are higher still because these races are a real world test of how the two parties are travelling less than a year out from the general election.

Labor needs to win Queensland seats like Longman and hold seats like Braddon if it is to take government. Failing to do that against a Coalition that has lost 36 Newspolls in a row would rightly send a shudder through party ranks.

And given the Coalition believes Bill Shorten is a drag on the Labor brand it is trying to make these races a referendum on the leader.

Not making him an issue in 2016 is seen by everyone from the PM down as the major flaw in the Coalition’s last campaign. The kill Bill strategy however might miss its mark.

Mr Shorten could lose both of these races and hold his job because Labor has toughened its rules on rolling a leader and because few in the party have the stomach for more bloodletting.

Others also judge that a leadership spill would cruel their chances of winning government – something Mr Shorten can still deliver, even if he stumbles at these hurdles.

Mr Shorten has proven to be a great campaigner and a canny politician who almost dislodged the government after a single term, so there would have to be a compelling case for change.

The sensible thing to do in the event of a loss would be to reassess and reboot – not mount a revolution.

But even a close run race will worry Labor hard-heads and confirm the recent trend in polling that suggests the Turnbull Government is mounting a comeback.

Newspoll, Essential and Ipsos now have the gap between the major parties set of just two points with the government trailing 49-51 after preferences.

This is a remarkable turnaround from the beginning of the year where senior Labor figures were told by their polling number crunchers that the government’s position was “irretrievable”.

Momentum is a powerful thing in politics. If the government scores a by-election win it will lift the party’s confidence, solidify the prime minister’s position and put Labor under enormous pressure.

So Labor puts a high price on winning these races and that can be measured. It has made $135 million in promises in Longman to the Coalition’s $41 million.

In Braddon it has splashed about $183 million worth of pledges to the Coalition’s $126 million.

So if promises are a measure of anxiety, Labor is just about twice as worried by the thought of losing these seats as the government is concerned about winning them.

Labor has also been spending up big on TV and radio advertising in Queensland.

The wildcard in the Longman race is One Nation. At the last election Pauline Hanson’s preferences saw Susan Lamb come from behind to beat the incumbent wunderkinder, Wyatt Roy.

One Nation preferences also elected a Labor MP in the Townsville-based seat of Herbert.

This time One Nation is running hard against Labor and published polling suggests the party has increased its share of the vote since 2016.

But that has mostly come at the expense of the Liberal National Party, so if the Coalition is to win Longman it will need to scoop up 60 to 70 percent of One Nation preferences. That seems like a big hurdle.

In Braddon Labor is running its health message hard. Its “Mediscare” campaign is credited with the late surge to the party in 2016 that unexpectedly delivered it three seats in Tasmania.

The story of Braddon is that it is older, poorer and more welfare dependent than the Australian average.

A third of its population receives some kind of Commonwealth benefit, which is well above the national average of 23 percent.

In short this population knows the value of government services better than most. If Labor’s health and education message does not cut through here, its gloss might be wearing off.

But with every party preferencing against the Coalition in this race, Brett Whiteley will have to get a primary vote of about 45 percent in order to be in the hunt. Again, that seems like a big hurdle.

So history and the balance of numbers seem to favour Labor but even a close result in both will force a lot of soul-searching.

It will be a nervous count for the Mr Shorten team and – if these races are very close – it’s possible we might not have a result on the night.

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