Battles over Israel are a defining feature of Democratic primaries across the country.

Now, the issue is coming to the fore in a Republican primary for a House seat in Indiana. The Republican Jewish Coalition is planning a significant campaign opposing former Representative John N. Hostettler, who served in Congress from 1995 until 2007, and is now running in the state’s Eighth District.

The R.J.C. has reserved $1 million for advertising on broadcast and cable television in the district to defeat Mr. Hostettler and support one of his opponents, State Senator Mark Messmer, said Matt Brooks, the R.J.C.’s chief executive.

“We want to send a message to everybody, loud and clear, that if you don’t stand with the Jewish community, if you don’t stand with Israel, Republican or Democrat, the R.J.C. is going to work to do what we can to defeat you,” Mr. Brooks said.

The airtime reservation begins April 10.

Mr. Brooks said Mr. Hostettler’s time in Congress reflected an “anti-Israel record.” He also voiced concerns about a book Mr. Hostettler wrote, “Nothing for the Nation: Who Got What Out of Iraq,” which has drawn criticism for using antisemitic tropes.

Mr. Hostettler did not immediately return a call seeking comment.

It is a notable example of Republicans policing their own on the subject of Israel, which has in recent years roiled many Democratic races, even before the war in Gaza.

Polls, however, show that Democrats are more divided in their view of Israel than Republicans, who largely see the country favorably.

United Democracy Project, the super PAC linked to AIPAC, a pro-Israel group, is also getting involved, rolling out a six-figure television ad campaign opposing Mr. Hostettler, Jewish Insider reported on Wednesday.

Indiana’s primaries are scheduled for May 7.

Mr. Brooks said the last Republican whom the organization advertised against was Steve King, a former Iowa congressman with a history of racist comments, who was defeated in 2020.

“We’re going to do everything we can not to allow anti-Israel voices to come to Congress,” Mr. Brooks said.