Simon Kuper of the Financial Times has details:
At least the US process is corrupted chiefly by homegrown US money. In many countries, foreign funds now do the job. Buying into other people’s political systems is a bright idea that is conquering the world. Various trends in globalisation have encouraged it: ever more countries hold elections; ever more major powers seek influence abroad; and ever more billionaires can afford to buy foreign elections.
For instance, Israeli prime minister Benjamin Netanyahu typically gets more than 90 per cent of his funding for his primary campaigns from American donors. In Britain’s coming European referendum, Goldman Sachs and other American banks are among the biggest funders of the anti-Brexit campaign. Meanwhile, says the OECD’s new report, Financing Democracy, “anti-Islam groups in the US have provided financial support to Dutch politician Geert Wilders . . . whose Freedom party is the least transparent Dutch parliamentary group and a rallying point for Europe’s far right.” A year before national elections, the Freedom party leads the Dutch polls.
But let’s not single out American money. “The Kremlin is working hard to buy off and co-opt European political forces, funding both rightwing and leftwing anti-systemic parties throughout Europe,” says US vice-president Joe Biden. France’s Front National borrowed €9.4m from the First Czech Russian Bank in Moscow. Even xenophobic parties love foreign money. The Greek far-right Golden Dawn took the well-trodden Balkan nationalist path of fundraising among the diaspora in Australia, stopping only after media kicked up a fuss.
Like global south-to-south trade, south-to-south political funding is growing fast. China likes to help out African ruling parties, says Patrick Smith, editor of the Africa Confidential newsletter. Officials of the African National Congress have long benefited from training at the Chinese Communist party’s leadership academy in Pudong. Now the ANC is creating a Chinese-inspired academy at home in Venterskroon. Possibly coincidentally, the ANC’s head of research discovered in the course of a Chinese study tour last year that China has “opposition parties, whose role was to assist the government to govern” — a model for South Africa’s “rowdy, noisy and disagreeable opposition”, he added, in a newspaper opinion piece.
Middle Eastern regimes have also got into the campaign-finance game. Qatar funded various Islamist movements in the Arab spring (mostly betting on losing horses).Here's a link to the OECD report that Kuper mentions.