Sometimes it's the biggest things that politicians don't want to talk about.

For Labor, that's the polls. Let's be clear, the opinion polls spell complete annihilation. Under the swings predicted in published polls Labor could lose between 26 and 30 of its 72 federal seats. In NSW it stands to lose 10 of its 25 lower house seats. In Queensland it is quite possible the former leader Kevin Rudd could be the only federal MP left standing.

To find another result that bad for the ALP, you have to go back to Labor's 1975 wipeout, its worst result in the postwar period, when the ALP's two party-preferred vote was 44.3 per cent, almost exactly where its two party-preferred vote is sitting in the opinion polls today.

The desperate hope inside the ALP is that two things might finally start to turn this dire situation around; the May 8 budget, and the imminent cash payments and tax cuts to compensate for the carbon tax.

Returning the budget to surplus is seen as the way to give voters reassurance that Labor has the economic management of the nation in hand (even though a strong majority say they think Tony Abbott would do a better job) especially if the government's actions can be linked in the mind of the electorate to the welcome relief of a reduction in interest rates.

But many senior members of the Labor caucus strongly doubt anyone is listening to anything Labor has to say. ''They feel betrayed, they don't trust us … as they say on the TV show, it's locked in Eddie,'' one MP said this week.

And the desperation of the caucus is only compounded by the fact that Labor's brutal leadership showdown in February so effectively accomplished what it was designed to do - it killed off the party's only ''plan B''.

These are not MPs in the defeated ''Rudd camp'', but rather people who voted for Julia Gillard and continue to support her. They simply acknowledge that what happened in February has left the party with no obvious way out of its existential dilemma.

Compounding Labor's problem is the dawning realisation that the scale of the defeat for which they are on track could also conceivably allow the Coalition to control the Senate.

Senior Labor strategists believe this is now a real possibility - if the usual split of three ALP or Green senators and three Coalition senators in each state instead became a 4-2 split in three states, perhaps including the loss of a Labor seat to Bob Katter's party in Queensland. Such a result would mean an Abbott government would be able to immediately and easily unwind all that the Rudd and Gillard governments have done.

It would also solve the problem the Coalition does not want to talk about - how it would make good Abbott's ''blood pledge'' to repeal the carbon tax.

This, Abbott says, would be the very first thing he would do as prime minister. And indeed, it would have to be. He's built his leadership and his success on the back of his campaign against it.

He says he would expect a defeated Labor Party to accept the will of the people and agree to repeal the tax, and, after a defeat of the magnitude that seems to be coming, that's possible, despite Labor's vehement denials that it would ever contemplate such a move. If things pan out this way Abbott could well achieve the demise of the tax inside his stated timeframe of six months.

But if Labor are true to their word, if the Senate does block Abbott's attempted repeal, and he is forced to call a double dissolution election, it is very unlikely he would be able to bring about the end of the tax within a year - his stated timetable for this eventuality.

Legal advice to both industry and environmental groups suggests it could take most of a Coalition government's first term, and that the process could become very messy.

The problems are both legal and practical.

Senators elected in a half-Senate election late next year do not take their seats until July 2014. Abbott's timetable is based on achieving the requirements for a double-dissolution election (two rejections by the Senate, three months apart) before that date, because once the senators change he would have to start the process all over again.

But the High Court has ruled the Senate must have ''a proper opportunity for debate'', which could make it tricky to get the requirements for a double-dissolution election in place before the Senate changeover in July.

Some, but not all, constitutional lawyers believe laws passed as a result of a quick double-dissolution election could be challenged on the basis that the new Senate was dissolved even before its members had a chance to take their seats. It would effectively be terminating the parliamentary terms of the old Senate and the newly elected Senate in one fell swoop.

The constitutional lawyer George Williams tells the Herald he thinks legislation passed after such a rushed double dissolution would be ''open to challenge'', even if the big practical problems of getting to a double-dissolution poll in time could be overcome.

Another constitutional lawyer, Greg Craven, says there is no legal problem, but believes the practical problems are huge.

"It is perfectly clear that there is no prohibition against a double dissolution being called between a half-Senate election and new senators taking their sets. No matter how unusual this might be considered, there is nothing in the words or logic of section 57 to prevent it,'' he says.

''Of course, the practical reality is that the extended time required to produce the necessary conditions for a double dissolution probably means the question is purely theoretical."

If either the practical, or the legal, does stand in Abbott's way, companies could continue to pay the carbon tax until 2015.

And now we know the new $10 billion Clean Energy Finance Corporation, which the Coalition has also vowed to scrap, would be in the same political situation. The full $10 billion will be appropriated in the legislation setting it up, meaning that to stop its activities, the Coalition has to achieve the legislation's repeal.

The possibility he would not be able to quickly kill the carbon tax is something Abbott would rather not talk about. But if Labor can't find an answer to its big problem - how to stave off landslide defeat - Abbott's problem might be solved.