Kentucky Secretary of State Trey Grayson (R) will have, at the very least, a well-funded Senate primary opponent in Rand PaulRand PaulGOP rep: Trump has 'extra-constitutional' view of presidency The ignored question: What does the future Republican Party look like? Rand Paul skeptical about Romney as secretary of State MORE.

Paul's campaign website reports that he has already raised more the $680,000 for the race, including $430,000 during a Thursday "moneybomb." The former total exceeds the amount Grayson raised for his exploratory committee in the second quarter and puts Paul on a very strong fundraising pace.

Paul is the son of former presidential candidate and Texas Rep. Ron Paul (R) and is tapping into the same type of fervor that helped his father raise lots of money for his long shot presidential bid.

The younger Paul is beginning to look like much less of a long shot, after a recent SurveyUSA poll showed him taking 26 percent of the vote, to Grayson's 37 percent.

Another libertarian-leaning Republican Senate candidate, Peter Schiff, is also raising big money in Connecticut.