For those states holding primaries, voters go to polling places and cast their ballots. In caucus states, voters gather in meeting places throughout the state to discuss candidates and reach a consensus on which candidate they will support.
| DATE | STATE | OUTCOME (top three finishers) |
| January 3 | Iowa (caucus) | Rick Santorum, 25 percent |
| January 10 | New Hampshire (primary) | Mitt Romney, 39 percent |
| January 21 | South Carolina (primary) | Newt Gingrich, 40 percent |
| January 31 | Florida (primary) | Mitt Romney, 46 percent |
| February 4 | Nevada (caucus) | Mitt Romney, 59 percent |
| February 4-11 | Maine (caucus) | Mitt Romney, 39 percent |
| February 7 | Colorado (caucus) | Rick Santorum, 40 percent |
| February 7 | Minnesota (caucus) | Rick Santorum, 45 percent |
| February 7 | Missouri* (primary) | Rick Santorum, 55 percent |
| February 28 | Arizona (primary) | Mitt Romney, 47 percent |
| February 28 | Michigan (primary) | Mitt Romney, 41 percent |
| March 3 | Washington (caucus) | Mitt Romney, 38 percent |
| March 6 | Alaska (caucus) | Mitt Romney, 33 percent |
| March 6 | Georgia (primary) | Newt Gingrich, 47 percent |
| March 6 | Idaho (caucus) | Mitt Romney, 62 percent |
| March 6 | Massachusetts (primary) | Mitt Romney, 72 percent |
| March 6 | North Dakota (caucus) | Rick Santorum, 40 percent |
| March 6 | Ohio (primary) | Mitt Romney, 38 percent |
| March 6 | Oklahoma (primary) | Rick Santorum, 34 percent |
| March 6 | Tennessee (primary) | Rick Santorum, 37 percent |
| March 6 | Vermont (primary) | Mitt Romney, 40 percent |
| March 6 | Virginia (primary) | Mitt Romney, 59 percent |
| March 6–10 | Wyoming (caucus) | Mitt Romney, 44 percent |
| March 10 | Guam (caucus) | Mitt Romney, 100 percent |
| March 10 | Kansas (caucus) | Rick Santorum, 51 percent |
| March 10 | Northern Mariana Islands (caucus) | Mitt Romney, 87 percent |
| March 10 | U.S. Virgin Islands (caucus) | Ron Paul, 29 percent |
| March 13 | Alabama (primary) | Rick Santorum, 35 percent |
| March 13 | Hawaii (caucus) | Mitt Romney, 45 percent |
| March 13 | Mississippi (primary) | Rick Santorum, 33 percent |
| March 20 | Illinois (primary) | Mitt Romney, 47 percent |
| March 24 | Louisiana (primary) | Rick Santorum, 49 percent |
| April 3 | District of Columbia (primary) | Mitt Romney, 70 percent |
| April 3 | Maryland (primary) | Mitt Romney, 49 percent |
| April 3 | Wisconsin (primary) | Mitt Romney, 43 percent |
| April 24 | Connecticut (primary) | Mitt Romney, 67 percent |
| April 24 | Delaware (primary) | Mitt Romney, 56 percent |
| April 24 | New York (primary) | Mitt Romney, 63 percent |
| April 24 | Pennsylvania (primary) | Mitt Romney, 58 percent |
| April 24 | Rhode Island (primary) | Mitt Romney, 63 percent |
| May 8 | Indiana (primary) | Mitt Romney, 65 percent |
| May 8 | North Carolina (primary) | Mitt Romney, 66 percent |
| May 8 | West Virginia (primary) | Mitt Romney, 70 percent |
| May 15 | Nebraska (primary) | Mitt Romney, 71 percent |
| May 15 | Oregon (primary) | Mitt Romney, 72 percent |
| May 22 | Arkansas (primary) | Mitt Romney, 68 percent |
| May 22 | Kentucky (primary) | Mitt Romney, 67 percent |
| May 29 | Texas (primary) | Mitt Romney, 69 percent |
| June 5 | California (primary) | Mitt Romney, 80 percent |
| June 5 | Montana (primary) | Mitt Romney, 68 percent |
| June 5 | New Jersey (primary) | Mitt Romney, 81 percent |
| June 5 | New Mexico (primary) | Mitt Romney, 73 percent |
| June 5 | South Dakota (primary) | Mitt Romney, 66 percent |
| June 26 | Utah (primary) | Mitt Romney, 93 percent |
* Missouri held a nonbinding primary on February 7 that did not select delegates to the 2012 Republican National Convention. Instead, the Missouri Republican Party held a caucus on March 17 to select convention delegates, and who the delegates choose will be announced after events in May and June.
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