With precisely four weeks to go, fasten your seatbelts.
The polls were steady for months.
The Washington consensus was that President Obama would coast to re-election because he had established a clear lead in some of the key battleground states like Ohio and Wisconsin.
So even if the popular vote was close, Obama would easily clinch the Electoral College and secure a second term.
But all of a sudden the polling has become much more favourable towards Mitt Romney and that is making the President's election strategists extremely nervous.
One poll in particular has caused a major tremor. Not an earthquake - not yet - but definitely a sign that some tectonic plates may be moving.
The Pew Research Centre poll shows that Romney has now moved ahead of Obama among likely voters by 49% to 45%. If that is confirmed by other surveys, it is astonishing. Other polls also reveal a post-debate bounce for Romney but not on this scale.
In addition some of the state polls are showing a big shift towards Romney.
Michigan, a state in which Obama had such a big lead that Republicans had given up, is suddenly back in play with the President now only narrowly ahead.
The biggest surprise of all to me is that the Republican candidate has completely erased Obama's huge 18-point lead among women voters.
In Colorado last week I went to a "victory rally" for Republican women held by Ann Romney.
None of those I interviewed believed Obama had a lead. They thought it was a liberal media conspiracy.
I was told by one Republican loyalist that women voters were like a quiet river that would suddenly burst its banks.
She was confident women would break for Romney at the last moment. The Pew poll suggests she may be right.
It all adds pressure to Team Obama in the next two debates.
The President needs to do much better than his lamentable performance in Denver.
But even before that, Vice President Joe Biden needs to steady the ship this week when he goes into the ring with Paul Ryan.
The bottom line: If Romney can keep up his post-Denver momentum, we have a race on our hands that could produce a very tense and unpredictable campaign.
- I will have more on these polls on News At Ten tonight.