Officially, Mr Lu Aihua retired from politics eight years ago. But as the campaign for Taiwan's local elections on Saturday reached fever pitch last week, Mr Lu received a visit from government investigators who are probing whether he is helping China interfere in the upcoming polls.

"The investigators are asking if the money the Chinese communists are paying me comes with instructions to back a particular candidate or a particular party in the election," says Mr Lu, an influential former lawmaker in the southern city of Tainan.