WHAT should have been Brexit Day has been postponed if not cancelled — and nobody will be celebrating more than Jo Swinson and her party, although she might be wise to keep the champagne on ice a little longer.

Better still, the Lib Dem leader should empty the ice-bucket over the head of her feverish deputy Sir Ed Davey.

He recently declared on LBC radio that the Lib Dems can win next month’s general election and put his boss into 10 Downing Street.

On second thoughts, perhaps Swinson should join Davey under the cold shower. She has told BBC Radio Four that her party is within a “small swing” of winning hundreds of seats on December 12.

How does she know? Local Lib Dem polling tells her so. Of course, anyone familiar with “local Lib Dem polling” knows that they bear as little resemblance to the truth as a Thomas Cook holiday brochure.

As householders across Britain can testify, on the eve of polling day a leaflet invariably drops through the letterbox with a bar chart showing the state of local opinion.

Surprise, surprise, the Lib Dem candidate is always neck and neck with the Labour/Tory/SNP/Monster Raving Loony Party incumbent, confirming that “only a vote for the Lib Dems can remove…” said MP or councillor.

In reality, Swinson and Davey must be seriously deluded if they believe their party has any chance of boosting its Commons tally from the current 19 to somewhere north of 300.

It’s certainly possible that the Lib Dems could win a few score more seats if singleminded pro-EU voters turn to them from other parties.

But how many ex-Labour supporters would be willing to do so, once they are reminded of the Lib Dem record as Tory-enabling, anti-working-class warmongers?

After all, Swinson’s Westminster voting record speaks for itself. She has gone into the lobby to support the bedroom tax, welfare and local council spending cuts, higher VAT, lower corporation tax on company profits and less access to legal aid and employment tribunals.

She opposed higher tax rates for the very rich, a bankers’ bonus tax and a mansions tax.

She voted for raising student tuition fees and the rip-off privatisation of Royal Mail.

She has upheld higher rail fares, voted against renationalising the railways and endorsed military action overseas in the service of US and British imperialism.

Not even Boris Johnson joined her in the lobby on top tax rates, tuition fees, VAT and the bedroom tax.

Jeremy Corbyn was on the opposite side to Swinson — and on the same side as progressive public opinion — on every one of these issues. That might explain her unbending hostility to him ever becoming prime minister.

In all of these matters, too, Plaid Cymru and Green Party MPs have declined to share a lobby with Swinson and the majority of her Lib Dem colleagues.

How extraordinary, therefore, that these parties are now considering an electoral pact to hand seats to the Lib Dems in England and Wales.

Yet not even this support and that of pro-Remain Tories will be enough to lift the Lib Dems above the 100-seat threshold. From that point, Swinson and co will need to dislodge sitting MPs with current majorities of 20,000 and more.

None of this, thankfully, will produce a Lib Dem government on December 13. All we can know for certain is that every vote and seat for the Lib Dems will weaken the prospect of winning a left-led Labour government whose domestic programme promises real change.