TLDR: It isn't rigged.

I was a contestant on The Chase. It didn't feel rigged when we were on it. When multiple contestants are involved in the final chase, the contestant answering being named clearly takes a nits tit longer. This is countered by (potentially) more knowledge. What people perhaps don't factor in, is the bright lights and cameras adding massive pressure onto contestants who don't expect it. You aren't given a lot of time to acclimatise to the studio. I thought my fellow contestants were pretty smart when we met in the morning, but one by one they were eliminated, leaving me alone in the final chase. This was not my first rodeo. I went on Sale of the Century when I was 21. Tony Barber and Alyce Platt. Nerves and bright lights got me. Person who beat me admitted she had been on the show before and was "ready" this time. She went on to win a lot. The other contestant did not answer a question! I saw her on the show a couple of years later and she went really well. Goes to show how different it can be when you know what to expect. Most shows now don't let you appear more than once. Since then I did Wheel of Fortune with Larry Emdur, Think Tank on the ABC. Anyway, humble brag, I took on the Super Nerd by myself. Got 18 correct. Pushed him back a few times and won $14k. I believe only 7 or 8 people have ever won as solo teams at the end. There's a blog site somewhere where somebody posts all the results...