US law prohibits candidates for any public office to accept donations from individuals or businesses that are not from the US. That is supposed to cut down on the influence of foreign powers on our government and electoral process. But in recent years, candidates have started going abroad and hosting fundraisers in foreign nations. Obama did this in his 2008 election, and raised about $700K from wealthy Americans who were living abroad.
This year, Romney is doing the same thing, and is in London right now to raise money for his campaign. His plan is to hold two fundraising events, which have high entry fees, and show support for the wealthy Americans living in that country. As with Obama, Romney's visit was echoed by wealthy domestic donors, who also made the trip so they could throw more money at Romney.
The problem with this trend, in my opinion, is that it looks more like a publicity stunt than a serious campaign strategy. In an age where a video can make its way around the world in seconds, borders seem a bit superfluous. Whatever Romney says in London will be heard almost immediately by people in the states. But it still seems to me that our presidential candidates have a tendency to show off by going on these trips, and spending large amounts of money to do it.
The other thing that bothers me about this is that I can't be confident that Romney or Obama will refuse money from foreign entities, whether they be businesses or individuals. I've heard people talking about how they check ID's and make sure a person is eligible to give money to the campaign, but I'm still not sure that will stop the campaigns from accepting cash under the table.