Nonetheless, both of his potential challengers say he is vulnerable.

A horse, though, was of a size to be considered a potential challenger.

The other potential challengers are looking for a sign.

That leaves Microsoft in a position once again to use its monopoly power to stop potential challengers.

But each potential challenger needs to make his or her own independent assessment of the times.

Some wonder if his uncle is a potential challenger; others see him as a protector.

Mr. Smith could not be reached for comment on his potential challenger.

By evening's end, though, he was warning away any potential challengers to his leadership.

Other potential challengers, including Peter King, never had a chance.

You are correct, US military spending has been far greater than any potential challenger.