According to the garrulous Simon Wheeler, Jim Smiley was willing to bet on anything. If he found someone who was willing to bet, he'd take him on. If the person didn't want to bet on the side Smiley originally proposed, Smiley was willing to change sides and bet against what he was originally going to bet for, just so he could bet. If there were birds sitting on a fence, he was willing to bet about which one would fly away first. He was even willing to bet that the parson's wife wouldn't recover--although that was probably just Smiley misspeaking. In the case of the jumping frog, Smiley's over-willingness to bet anyone on anything worked to his detriment. Smiley had a prize jumping frog, Dan'l Webster, that he had trained to jump farther than the typical amphibian. One day a stranger came to town, and Smiley invited him to put up a frog against Dan'l Webster. The stranger said he would, if only he had a frog of his own. This temptation proved too great for Smiley, who was only too willing and eager to find the man a frog to use. While Smiley was out catching a frog for the stranger, Smiley unwisely left Dan'l Webster in the presence of the stranger. The stranger "prized open his mouth and took a teaspoon and filled him full of quail shot--filled him pretty near up to his chin." When Smiley returned with the other frog and the challenge began, Dan'l Webster couldn't budge, to Smiley's surprise and disgust. The stranger took his winnings and left before Smiley realized how he'd been taken. Smiley's willingness to bet on anything had caught up to him in that instance.
In this story, Jim Smiley is the most compulsive gambler you could ever hope to meet. So I would say that what he is willing to do is to bet on just about anything.
One of the things he likes to bet on is his jumping frog. He has it trained to jump really well and he thinks it can beat anyone else's frog. What happens to it is that he bets someone that it can outjump that guy's frog. While Smiley is out finding a frog for the guy, they guy fills Smiley's frog up with lead shot. That makes the frog unable to jump and Smiley loses the bet.