Much of the political universe is focused on the results this Tuesday in Ohio and Florida, the delegate-rich states that could determine whether Donald J. Trump can clinch the Republican nomination soon or if the race is bound to remain unsettled until the convention in July.

But Senator Ted Cruz of Texas is shifting his focus this weekend away from Ohio to such far-flung Missouri communities as Ballwin, Cape Girardeau and Springfield.

With Mr. Trump leading polls in Florida, Gov. John Kasich battling Mr. Trump for supremacy in Ohio and his own team increasingly convinced that the race will become a grinding delegate battle across all 50 states, Mr. Cruz has decided to seek votes in places that offer the best chance to deliver him delegates on Tuesday.

In addition to his appearances on the stump, Mr. Cruz’s campaign is aiming its television and online advertising, and its volunteer door knockers and phone bankers, at potentially overlooked areas, hoping to amass enough delegates to deny Mr. Trump an insurmountable advantage in the race.