This site argues that the time to start backing challengers in the 2010 election is now:
Early funding also has a snowball effect — since people usually don’t want to throw their money away, they’ll generally only support a candidate who seems to have a chance to win. Before insurgent candidates can get much outside attention, they have to hit a threshold of support that indicates that they’re a serious contender. They have to have enough of SOMETHING — money, polling numbers or on-the-ground organization — to convince outsiders to get involved. And without resources and expertise available early, many candidates who might actually have a shot if given a chance never quite hit the mark. A handful of paid staff, or even just ONE paid staffer, can create the relationships and the organization that a campaign needs to prove viability, while also getting the structure in place to actually take real advantage of any money that floods in at the last minute.
I agree with this completely. Read the whole thing. Unfortunately, I don’t get the impression the GOP in my district is floating a challenger to Murphy yet. Hopefully they won’t wait until it’s too late.