Iowa state Sen. Brad Zaun (R) is hinting at a run as an independent congressional candidate this fall, a move that could fatally damage Republican hopes of holding retiring Rep. Tom Latham's (R-Iowa) seat.

Zaun finished first in the GOP primary, but with less than the 35 percent needed to win the nomination. The GOP's nominating convention then picked former Capitol Hill staffer David Young (R) over Zaun, who had been the party's 2010 nominee for a similar House seat.

Now Zaun is threatening to bolt from the party.

"As we celebrate Independence Day," Zaun wrote on Facebook Friday evening, "several of my friends that are encouraging me to switch to an Independent. What do you think? Very frustrated as Republicans lost their way!"

The race in the southeastern Iowa swing district is a top target for both parties, and Zaun could pull votes from Young and hand the race to Democrat Staci Appel.