President Barack Obama's visit to shore up support for the EU has become incredibly divisive.
But aside from whether or not Obama is right to speak up or acting hypocritically, the real question is will he be successful in urging Britons to vote for continued EU membership?
Downing Street clearly think he's going to have an impact, and bookies have found the Prime Minister might be right to have made so much of the visit.
Ladbrokes say that the chances of Brexit have diminished sharply today as Obama weighted into the debate.
It says 90 per cent of all bets in the last 48 were for Remain, and the prospects of a Leave verdict dived from 34 per cent to 29 per cent as punters rushed to back the status quo.
"This is the biggest betting shift of the campaign so far. Treasury reports, Boris Johnson and David Cameron have hardly shifted the dial, but the moment President Obama's feet touched the ground in the UK, the chances of a Brexit vote took a big hit," Matthew Shaddick of Ladbrokes said.
And Betway reported the odds of remaining in the EU to have shortened. Odds for remaining in the EU have shifted from 4/9 to 4/11.
Meanwhile, the bookie's odds on Brexit have moved from 13/8 to 2/1 today.
Betway’s Alan Alger, said: "President Obama’s passionate intervention in the Brexit debate caps the Remain camp’s strongest week of the campaign so far, and triggered a flood of bets backing In."
"Yet, there are still two months to go until polling day and Brexit-backing Boris and Co. will be hoping that Remain have played their trump cards far too early. Will voters remember Obama’s words when in the polling booth? Only time will tell."
So, while Obama's visit may well have upset Boris Johnson and Nigel Farage, it may pay off dividends for Cameron.