BROOKFIELD, Wis. (AP) — Well-traveled routes that serve as Wisconsin's vital arteries also provide a window into the competing hopes for Mitt Romney and Rick Santorum.

Romney can roll up a solid win in Tuesday's presidential primary with a strong showing along the state's east-west Interstate 94, which bisects Milwaukee's GOP-rich western suburbs.

Santorum's fading hopes rest on swamping Romney in cities and towns along north-south Interstate 43, which lead from Milwaukee north through the industrial and blue-collar base of the Fox River valley.

Wisconsin election officials are projecting 35 percent of Wisconsin's 3.27 million voters will participate in Tuesday's primary. A large majority of the vote will come from Wisconsin's metropolitan southeast corner and industrial Fox Valley north to Green Bay.