A week after Arkansas Senator Mark Pryor was left without a Republican challenger, the GOP failed to field a major candidate to face Iowa Senator Tom Harkin, dealing the embattled Senate Republican caucus another blow. Harkin, running for a fifth term in the Senate, will face either a former state representative or one of two businessmen running in the GOP primary.

None of the three potential challengers are seen as a threat to Harkin, who has a long history of beating back well-funded and well-known GOP opponents. In his elections to the Senate, he defeated an incumbent Republican in 1984, then held off Republican members of Congress in 1990, 1996 and 2002.

The NRSC had hoped another member of Congress might make the race. NRSC chairman John Ensign hinted that a major recruit was poised to run in an interview earlier this year with Politics Nation, but both Reps. Tom Latham and Steve King declined a bid.

Their hesitancy may have been well-founded. Harkin, who raised and spent almost $7 million in 2002, had already pulled in nearly $4 million through December, FEC reports show. Steve Rathje, one of the businessmen running against him, had raised only $70,000 through the end of 2007 and had just $58 -- not a typo -- on hand. (Full disclosure: Part of that money went to pens bearing Rathje's name, one of which sits on Politics Nation's desk)