Kentucky Secretary of State Trey Grayson (R) will have, at the very least, a well-funded Senate primary opponent in Rand PaulRandal (Rand) Howard PaulCongress must end American support for Saudi war in Yemen Black men get longer prison sentences than white men for same crimes: study Sarah Palin on sexual harassment: 'People know I'm probably packing' so they 'don't mess with me' 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.