WASHINGTON--Presidential candidates have been doing it for years.
They raise money and explore their viability long before they announce they're running. And that practice is increasingly trickling down to the House and Senate level.
The latest example comes from the Montana Senate race, where Republican candidate Russell Fagg won't have to disclose any of the money he's raised until January -- seven months after he formed his exploratory committee for Senate this summer.
That's because he didn't officially become a candidate until October, in the fourth quarter of 2017.
But Democrats have argued that Fagg, who's running in a crowded GOP primary to take on Democratic Sen. Jon Tester, was acting like a candidate well before October. A liberal group has filed a complaint against him with the Federal Election Commission. Fagg recently hired a lawyer to respond to the allegations from the American Democracy Legal Fund.
Anyone who has decided to run for office or is actively campaigning must register with the FEC as soon as they've raised $5,000. Reaching that fundraising threshold triggers an official candidacy, which requires regular FEC reporting.
But exploratory committees, like Fagg's, allow people to explore the possibility of running for office -- and raise money to do so -- without having to register with or report to the FEC.
It's called "testing the waters," and FEC regulations around doing so are murky at best.
"This is a Byzantine area," said election lawyer Michael Toner, a former chairman of the FEC.
Potential candidates use exploratory committees in one of several ways. In the first instance, candidates sometimes open campaign committees and call them exploratory committees.