Michigan and Arizona Republican primaries (14 images)

Republican presidential hopeful Rick Santorum holds up a block of shale as he speaks to supporters at a primary election night rally on February 28, 2012 in Grand Rapids, Michigan. Both Michigan and Arizona held their primaries for the GOP presidential nomination on Tuesday. UPI/Brian Kersey

Supporters cheer Republican presidential candidate Mitt Romney at a campaign rally at the Suburban Collection Showplace in Novi, Michigan on February 28, 2012 upon the results of the Michigan Republican Primary. UPI/Santa Fabio

Republican presidential candidate Mitt Romney speaks to his supporters at a campaign rally at the Suburban Collection Showplace in Novi, Michigan on February 28, 2012 upon the results of the Michigan Republican Primary. UPI/Santa Fabio

Lynn Keenan, sister of Republican presidential candidate Mitt Romney waits for her brother to speak to his supporters at a campaign rally at the Suburban Collection Showplace in Novi, Michigan on February 28, 2012 upon the results of the Michigan Republican Primary. UPI/Santa Fabio