BORIS Johnson is from today a lame duck Prime Minister.

The North Shropshire by-election was presented in Tory circles as a referendum on Johnson's performance, and he lost miserably.

Two years ago voters in England's Brexit heartlands saw him as the leader who "got Brexit done" and the man who brought about their freedom from the "wicked dictatorship" of Brussels.

Now they think he's an incompetent buffoon engulfed in sleaze and scandal.

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He has gone from hero to zero, becoming as personally toxic in once ultra-safe Tory constituencies in England as he has been in Scotland for years. 

But what does Thursday's by-election result mean for his exit from Number 10, for the SNP and for independence?

Reports suggest we're not going to see Johnson make a speedy departure from Downing Street.

Many members of the 1922 committee of Conservative backbenchers may be desperate to send in their letters right away to Sir Graham Brady (as Roger Gale has already done) to trigger a leadership election, but to my mind circumstances and hard politics mean they will restrain themselves for a few months.

Tory members don't want to see a leadership contest under the dark cloud of the Omicron Covid variant. 

READ MORE: North Shropshire: Tories give Boris Johnson a stark warning after huge defeat

Conservative MPs will wait until sunnier, brighter days when the latest dire stage of the pandemic has subsided and life has returned to more normal times before pouncing.

There is talk in Tory circles of a summer leadership election. 

However, there is a chance if polls continue to be poor for the party there will be anxiety about whether Johnson's unpopularity could damage Conservative prospects in the local council elections in May. More Downing Street scandals could bring the timing of a leadership election forward.

Another factor on how long Johnson remains in Number Ten will be the timescale for the next General Election.

It is due to take place by May 2024 under the Fixed Term Parliament Act of 2011 that sets a specific date for elections to take place - but the UK Government is in the process of repealing this law. So whoever is PM will be able to call an election whenever they like - up to 2024.

It would be in the Tories' interests to go into the next General Election during their new leader's honeymoon period - which probably lasts around a year.

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If an election was to be held say in September 2023, the ideal time for the Tories to have a new leader and PM in place would be by the end of summer next year.

The bookies' favourite to succeed Johnson is currently Rishi Sunak. He has managed so far to keep away from party gate and other scandals and is in the minds of voters associated with the popular furlough scheme.

In terms of the SNP and independence, Johnson's fall will create the need for fresh thinking and strategy. 

Johnson has been dubbed by both Yes and No voters as the best "recruiting sergeant" for independence, the SNP's popularity in part based on Johnson's personal unpopularity.

The last Westminster election, and to a lesser extent the Holyrood one, was framed by the SNP as a hard choice between Nicola Sturgeon and the SNP - and Boris Johnson and the Tories.

SNP activists insist multi-millionaire Sunak is simply as unpopular as Johnson and his demise presents no problems. I'm not convinced.

Polling evidence suggests that Sunak (below) is significantly more popular than Johnson particularly among undecided voters in Scotland.

The National:

JL Partners, the firm led by Theresa May’s former pollster James Johnson, in October last year gave the Chancellor a net popularity rating of +30 with Scottish swing voters.

The same survey of 1016 voters gave independence a 56% to 44% lead (excluding those who said they did not know) and found Johnson’s leadership the biggest factor driving swing voters in Scotland towards backing independence.

So while many voters across Scotland - and the UK more generally - will celebrate Johnson's fall, his exit will pose fresh challenges too for the SNP. 

The worry for the party must be whether their popularity will suffer when Johnson finally leaves Number 10 and is succeeded by a new Tory leader, one perhaps more palatable to Scots.

It will be fascinating to see when Johnson goes, who becomes the next Tory leader and how the SNP reframe their arguments. 

Christmas is still to come and the New Year promises plenty of political excitement.