Betting can come in any form, as long as its part of what constitutes an invent, a program or a game to bet on...
Anything can constitute an item of bet and that's what makes betting/gambling abstract in the sense of no exchange of goods is involved unlike what's in trading. It's a fantasy (so to say) to be satisfied and that's how sites come up with the mechanism to enable bettors satisfy themselves. It's not a bad idea including political events on betting sites. At least that should get bettors to be politically aware of their surroundings too. I like the idea.
Actually bookies doesnt really include politics kind of lines just because they do want to have some awareness about political side of things but rather they are really just that simply included all the things on which they do know that they could make money into or they would really be spreading out or would really be included on whatever things on which they could see that they could be able to make money from.
On personal point of view about betting on politics then it will really be always getting in line with someones personal point of view or choice on whom they do want to become the president or whatever that do talks about candidacy and it will really be just that basing up on what you choose and your bet will really be that basing or would really be according into that one.