Why, simple, because conservatives will not rally behind the leading conservative in the primary.
and also:
The Fix - Can the party establishment deliver in Tuesday's primaries?
The Republic - GOP challengers hope May primary brings in new wave of conservative leaders in IndianaThe Republic said:But the crowded field — which also includes financial adviser Don Bates Jr. of Winchester and Fishers businessman Richard Behney — will help Coats by splitting votes, said Nate LaMar, who organized a debate of the five Senate candidates in Henry County in February.
and also:
The Washington Post said:The most obvious example is in Indiana where former Sen. Dan Coats was recruited into the contest by national Republicans but has struggled badly to consolidate his frontrunner status. Coats' saving grace may well be that grassroots conservatives appear to be splitting their votes between former Rep. John Hostettler and state Sen. Marlin Stutzman