Most probably the bodyguard bet on the opposing candidate, LOL.. It's not that it's not allowed but I think as a sign of respect, just don't bet on the result of the election when you are serving someone, or if you will bet, you have to make sure it's done in silent. Betting on a certain candidate to win or loss might be easy since the candicate can get an inside information, and as a candicate, they also have their own survey and that information maybe vital enough to determine their chances of winning.
No matter what, that bodyguard must now show that he bet on the opposing candidate from other people. He must show that he is not interesting to place a bet for the Election. He can asks his friends or family to place a bet, but without anyone else knows so he will not doing a wrong thing. But that depends on himself because some people will not do that for his benefits and he only wants to do his job.
Betting on a certain candidate by secret can be done if he wants to take the benefits and he doesn't have loyal to the candidate or he just wants to make money from the Election. We can't blame him because he can bet by secretly without anyone know. After all, that will be up to him.
You said it so, about the morale. They're working with the government and they shouldn't do that. It might not be on the books but that should be understood that they must not gamble just as what they knew first before anyone else. Well, just as said, he shouldn't take any money from that bet and the bookie shouldn't reward him on that case.
The morale can not be bought with money. If someone loyal to one of the candidates, he will not place a bet even he will not lets his relatives takes benefits from what he knows. Besides that, they are working as bodyguard and must guard the Election not to place a bet.
They can separate where the fun things and the work. They don't wants to gets themselves in trouble so they will not tells other people even if they know something. That will not break their unwritten rules so they can feels calm when they work.