The Iowa Republican says Young has quit his job, has hired consultants and is in the process of buying a house outside of Des Moines. Many of those consultants have ties to Grassley, including famed GOP ad maker Fred Davis, who's best known for Christine O'Donnell's "I'm Not a Witch" ad but who's had a string of successes, including Rep. Steve King's (R-Iowa) 2012 reelection campaign.

Young will join former U.S. Attorney Matt Whitaker (R) in the race. Other potential GOP candidates include Secretary of State Matt Schultz (R) and Iowa state Sen. Joni Ernst (R). A number of higher-profile Republicans have taken a pass on the race, leaving local strategists nervous about the strength of the GOP field.

On the Democratic side, Rep. Bruce BraleyBruce Lowell BraleyOPINION | Tax reform, not Trump-McConnell feuds, will make 2018 a win for GOP Ten years later, House Dems reunite and look forward Trump: Ernst wanted 'more seasoning' before entertaining VP offer MORE (D-Iowa) is the likely nominee to replace retiring Sen. Tom HarkinThomas (Tom) Richard HarkinSenate GOP rejects Trump’s call to go big on gun legislation Trump should require federal contractors to follow the law Orrin Hatch, ‘a tough old bird,’ got a lot done in the Senate MORE (D-Iowa).