Donald Trump was seeking to regain momentum in the Republican nomination race today.
The presidential hopeful split four contests with rival Ted Cruz on Saturday.
This came after the Republican frontrunner endured a week of attacks from the party's establishment.
Four states voted on Tuesday, with Michigan the biggest prize up for grabs. The other states voting were Mississippi, Idaho and Hawaii.
Most opinion polls gave Trump a double-digit lead over Cruz and Ohio governor John Kasich in Michigan.
On Saturday, Trump narrowly beat Cruz in Louisiana and Kentucky, while Cruz convincingly defeated Trump in Kansas and Maine.
Florida senator Marco Rubio came third in three states and last in Maine, where he didn't garner a single delegate.
Tuesday also saw Democrats voting in Michigan and Mississippi.
Frontrunner Hillary Clinton has a solid lead in Michigan opinion polls over her rival, Bernie Sanders.
Large wins for Trump and Clinton would set them up for a potentially decisive voting day on 15 March in Ohio, Florida, Illinois, Missouri and North Carolina.