Political editor Ian Dunt believes UKIP's Paul Nuttall and Conservative Theresa May are the favourites to win their respective leadership races.
Nigel Farage resigned on Monday, and while many believe Paul Nuttall will become the new leader, Suzanne Evans has also declared her interest, despite being suspended from the party for being disloyal.
"Paul Nuttall is the more compelling proposition for UKIP, just because when he talks he sounds almost weaponised to pick up Labour voters," he told Julia Hartley-Brewer.
"I suspect they could do quite well with Nuttall and go quite far. Suzanne Evans, if she finds her way back into the party, which I suspect she probably will, is an accomplished media performer but she's a bit more stern.
"It has to be said it's quite hard for them to calibrate that approach when Westminster is in such a state, because if in a month's time Jeremy Corbyn is still leader, or if it's someone else, those are two very different situations UKIP has to deal with."
MP Andrea Leadsom is a Conservative candidate for leadership, but Dunt does not believe she's likely to win the election.
"Apparently she went all around the playground and started talking about all sorts of subjects [in her speech]," he explained. 'I'm quite surprised by the amount of praise that's been thrown her way, she has a mixed track record on this sort of stuff.
"Her view on minimum wage is really small firms should be able to pay whatever they want and get rid of people whenever they like.
"She wants all websites to be vetted by the BBFC the film censors, which is one of those bizarre opinions when you're a backbencher you get to come out with as many as you like, but when you're in the leadership it's really about credibility.
"Theresa May has been in Parliament since 1997, she's worked diligently, she's been at the top of politics if a long time," he added. "Going up against that kind of professional machine, it's going to be a bit of a problem for Leadsom."