YORKVILLE, Ill.  Two years ago, Republicans in this traditionally red district west of Chicago winced as a political newcomer rode a wave of Democratic enthusiasm and secured the seat held by J. Dennis Hastert, the long-serving former House speaker who had recently retired.  But now, just before a Republican primary on Tuesday, conservative voters here in the 14th Congressional District are scrambling to pick a challenger who might be able to capitalize on a wave of enthusiasm of their own and eventually reclaim the seat from the incumbent, Representative Bill Foster.  The issue of which candidate to choose  Ethan A. Hastert, a lawyer, political newcomer and son of the former speaker, or Randy Hultgren, a veteran state senator and financial adviser  has consumed the quiet counties west of Chicago that make up the district, as the candidates’ anti-abortion, antitax, small-government platforms are nearly identical.  “They’re so very close that you could wonder, ‘What’s the difference?’ ” said Mike Kenyon, a farmer who is chairman of the Kane County Republican Central Committee.  As a result of their similarities and the competitiveness of the contest, the race has turned personal. Mr. Hastert, 31, is being cast by his critics as the entitled son of the establishment, while detractors of Mr. Hultgren, 43, say he is representative of the dysfunction that is commonplace in the state capital.  The negativity has increased over the last few weeks. Mr. Hultgren spent some of his limited time at a forum in Yorkville a few days ago apologizing to Mr. Hastert, whose law firm he had accused in a piece of direct mail of representing companies with a history of human trafficking. In turn, Mr. Hastert had had his wife, Heidi, record an automated call in which she accused Mr. Hultgren of exploiting the suffering of women and children to further his political career.  “When that campaigning came out against Ethan, that probably hurt Randy,” said Ken Toftoy, a coroner who is chairman of the Kendall County Republican Central Committee. “Then Ethan had his wife get out there with a robocall. I’m not sure if that helped or not.”  Mr. Kenyon added: “It’s gotten a little ugly this time. There’s a bit of name calling. It’s on both sides.”  Many Republicans lament the situation because they believe that it was infighting the last time around, in the 2008 Republican primary between the businessman James D. Oberweis and State Senator Chris Lauzen, that helped clear the way for Mr. Foster’s victory in the special election to replace the elder Mr. Hastert. (Mr. Oberweis won the primary.)  So far, Mr. Hastert, buoyed by his father’s connections, has shown the greater fund-raising prowess. Newt Gingrich, the prominent Republican and former House speaker, for instance, headlined a campaign benefit for Mr. Hastert last month. The campaign reported having raised more than half a million dollars as of Jan. 13, in a filing to the Federal Election Commission.  Mr. Hultgren, in comparison, reported having raised $185,000.  But Mr. Hultgren has perhaps a slight edge on field organization, as he turned over about 300 more signatures than Mr. Hastert when filing to run for the seat. And he has received the endorsements of the major Chicago newspapers.  “This is not the Foster seat; it’s not the Hastert seat,” Mr. Hultgren said at the recent forum, channeling Scott Brown, the newly elected Republican senator from Massachusetts who used similar language to counter the notion that the seat long held by Edward M. Kennedy belonged to the Democrats. “We need someone with proven conservative leadership experience, not entitlement, to be able to represent us and lead us.”  Mr. Hastert says experience “cuts both ways” for voters.  “They see what has gone on in Springfield over the last decade or so,” he said, “and that’s certainly not the kind of experience they want in Washington.”  Mr. Hastert is on leave from his job as a commercial litigation lawyer at the Chicago firm Mayer Brown. He lives in the town of Elburn with his wife and their 3-year-old son. For a couple of years after he graduated from college, he worked at the White House as a special assistant to Vice President Dick Cheney’s chief of staff, I. Lewis Libby Jr.  “I grew up paying attention to policy and politics,” Mr. Hastert said. “It’s no stranger to me.”  Mr. Hultgren, who lives with his wife and four children in Winfield, says he is the man to beat Mr. Foster, having been elected to public service for more than a decade. “Talk is cheap,” he said. “People need to see real action. That’s what past public service brings. It’s more than just talk.”  The National Republican Congressional Committee has not endorsed either candidate.  “I think they’re right down the middle right now,” Mr. Kenyon, of the Kane County Republicans, said of the closeness of the race. “It’s going to be very exciting.”  Emma Graves Fitzsimmons contributed reporting from Chicago.
With the candidates’ positions similar, a primary between Dennis Hastert’s son and a veteran lawmaker has turned personal.