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What was that film called? As Good As It Gets? That's how Donald Trump must feel now that the attorney general has published his four-page summary of the Mueller report.

It is impossible to over-emphasise the significance of what has been said.

If the Democrats want to remove this president from the White House, it's going to have to be via the ballot box in November 2020, and not before.

The cloud that has been over the president for 22 months has gone, the weight that has sat on his shoulders has been lifted.

This is without doubt the best day that Donald Trump has had since his inauguration in January 2017. So let's go through it.

The Mueller investigation came in two parts - firstly, the question of whether there had been collusion between his campaign and the Russians.

On that there is 100% exoneration. Special Counsel Robert Mueller found that his campaign did not conspire or coordinate with Russia. That issue is put to bed.

On the question of obstruction of justice there is a bit of ambiguity.

Mr Mueller has a very interesting sentence: "While the report does not conclude that the president committed a crime, it also does not exonerate him."

But that has been looked at by the attorney general and William Barr reaches this conclusion: "Deputy Attorney General, Rod Rosenstein and I have concluded that the evidence developed during the Special Counsel's investigation is not sufficient to establish that the president committed an obstruction of justice offence."

Media playback is unsupported on your device Media caption Mueller report a "complete exoneration", says US President Trump

So in the eyes of the AG, Trump is in the clear there too.

That area of ambiguity is what the Democrats are going to focus upon. And here again, I am going to try to break this down into two parts. The first legal, the second political.

Legally, the House Judiciary Committee will want to get its hands on the full Mueller report.

They will want to see why Robert Mueller felt he couldn't exonerate the president on obstruction of justice.

And remember, obstruction of justice is one of the so-called "high crimes and misdemeanours" that can lead to impeachment.

There will be an endless back and forth over that. And I wouldn't be in the least bit surprised if the subpoenas start to fly.

Committees have the right to call people and papers. They are bound to flex their muscles as much as they can. They want to play this long. They want to damage the president.

To prosecute the president for obstruction of justice there would have needed to be evidence of intent to obstruct. So even though the president fired former FBI chief James Comey and unleashed regular torrents of abuse on Twitter about the investigation, if his only motivation for those acts was to vent his spleen rather than break the law, then he's done nothing wrong legally.

There is, of course, separately, a series of other criminal investigations going on into different aspects of the Trump Organization - the foundation, the inauguration committee, even the way the Trump Organization might have inflated or deflated insurance values on how much properties are worth.

They will run their course. But make no mistake the greatest single piece of jeopardy came from the verdict of the Mueller report, and the interpretation that it amounts to a "not guilty" is an enormous fillip to Donald Trump.

Now let's consider the political.

Media playback is unsupported on your device Media caption Jon Sopel: 'The headline is the president is in the clear'

It seems to me that while it is totally understandable that the Democrats are going to plug away - and in some ways it would be an abdication for an opposition party not to, and they may well do the president further damage - the risk associated with this course of action is bigger than any opportunity it presents.

Public opinion is going to watch the network news bulletins tonight, look at the news websites after this exhausting 22 month process, and think "OK, that's it. Move on."

How many ordinary people (a phrase I hate, but forgive me) would read the entire Mueller report with its endless appendices, even if it was released in total?

I suspect not that many. And we all have busy lives and limited attention spans.

The most successful politicians acknowledge that. A significant part of the voting population is just going to think "Thank goodness that's over."

The danger for Democrats is exactly the same as Republicans faced over the impeachment of Bill Clinton.

Despite his perjury and lies, President Clinton left office in 2000 with incredibly high approval ratings.

Why? Well, partly the economy was soaring. But also Democrats were repulsed by what they saw as political game playing by Republicans who were perceived to be putting their own political interests ahead of the country.

And the feeling was - to use a word that Donald Trump is fond of - that the Republican Party was conducting a witch-hunt.

Senior Democrats in Congress have always been aware of going down the impeachment route. But now they need to consider the risks of giving the appearance of being more interested and focused on bringing down the president than in the issues of ordinary people - health, work, salaries, college fees, schooling, the opioid epidemic etc.

Donald Trump is, as I write this, aboard Air Force One on his way back to Washington.

If he wasn't teetotal, I feel sure he would be uncorking the champagne. Maybe he'll have a celebratory Diet Coke with an extra cube of ice.

He always said it was a hoax and a witch-hunt. And not surprisingly he says he has been totally vindicated.

Shifting that narrative, much as the Democrats will try, is going to be immensely difficult.