The Conservatives are going on the attack as polls make for grim reading for Cameron

David CameronREUTERS/Leon Neal/PoolBritain’s Prime Minister David Cameron gives a speech at an election rally at The Corsham School in Chippenham, south west England, March 30, 2015.

The Conservatives came out swinging on Thursday as polls suggest the party will struggle to gain enough seats to form a government after May’s General Election.

Defence Secretary Michael Fallon launched a personal attack on Ed Miliband accusing him of having stabbed his own brother in the back” in an article written for The Times. He suggested that the Labour leader would do the same to Britain by caving in to the SNP and abandoning plans to build four new Trident nuclear missile submarines.

In response, Miliband accused Fallon of “demeaning himself and demeaning his office”:

Yet these types of attack are increasingly becoming the norm rather than the exception as the campaign for Number 10 enters its final four weeks. Elsewhere on Twitter, the Conservative Party press office’s official account took on Damien McBride, the former Whitehall civil servant and former special adviser to British Prime Minister Gordon Brown, for what looked to be fairly light criticism of the party’s electoral strategy.

Even McBride, who has been in his fair share of bruising political debates, seemed rather taken aback:

So why the sudden shift into attack mode?

Well, a possible proximate cause could be the most recent polling done by Lord Ashcroft of Conservative marginals. The results suggested that four of the 10 constituencies polled looked set to fall to Labour, with another effectively tied between the two parties.

Although the implied swing to Labour, if reflected across the country as a whole, would fall far short of providing Miliband with anything like an outright majority, any signs that these key swing seats are vulnerable could be enough to change the tone of the Conservative campaign. The primary reason is that, while the SNP has effectively pledged its support for a Labour government, if the Tories fail to win a majority in their own right (an outcome that is now extremely likely) it will have to rely once again on the Liberal Democrats.

And, with Liberal Democrat support having more than halved over the course of this parliament, that is not a comfortable place for them to be. Even if Nick Clegg’s party outperform expectations on May 7 and win 30 seats, Cameron will still be left needing around 300 to hit that magic 326 number for a functioning government in a Con/Lib coalition.

Below are the latest projections from independent political forecasters Election Forecast UK:

Here’s the problem — (Con) 284 + (Lib) 28 = (Con/Lib) 312

(Lab) 274 + (SNP) 41 = (Lab/SNP) 315

Even if the Tories secure DUP votes they would still, on the above numbers, fall agonisingly short of the 326 number required:

(Con) 284 + (Lib) 28 + (DUP) 8 = (Con/Lib/DUP) 320 — still 6 short

However, if the Lib Dems chose to join a Labour-led coalition with SNP support on a vote by vote basis you get this:

(Lab) 274 + (SNP) 41 + (Lib) 28 = (Lab/Lib/SNP) 343 — comfortably over the line

On this basis the Conservatives require at least 290 seats in order to stand a chance of forming a government after May, while Labour need around 270 to do the same. Given that the two parties are effectively neck-and-neck in the polls, this augers ill for Cameron’s hopes of getting the keys back to 10 Downing Street.

So if we see the Conservatives continue to aggressively take the fight to Labour over the next few weeks, this is very likely to be the reason why.

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