May 5: The first of more than a dozen GOP debates is held in Greenville, S.C.
May 11: Newt Gingrich enters the race
May 13: Ron Paul begins his third presidential campaign
May 15: Gingrich dismisses the House GOP budget as "right-wing social engineering"
May 21: Herman Cain enters the race
May 22: Indiana Governor Mitch Daniels says he won't run
May 23: Tim Pawlenty enters the race
June 2: Already leading in the polls, Mitt Romney enters the race
June 6: Rick Santorum enters the race
June 9: Top Gingrich staffers resign after the candidate goes on a cruise to the Mediterranean
June 13: Pawlenty stumbles in a debate when he declines to repeat his criticism of Romney's health care reform as "Obamneycare"
June 21: Jon Huntsman Jr. declares his candidacy
June 27: Michele Bachmann enters the race
'Corporations are people, my friend.'
--Romney, rebuffing a heckler who suggested raising taxes on businesses rather than individuals
July 6: Romney's campaign announces it has raised $18.5 million, dwarfing the competition
July 8: Bachmann and Santorum sign a pledge implying that African-American children were better off under slavery than they have been since President Obama's election
July 15: The Gingrich campaign admits it's $1 million in the hole
July 16: Rick Perry electrifies the conservative base with hints that he will run
'Under President Bachmann, you will see gasoline come down below $2 a gallon again. That will happen.'
--Bachmann, flush with confidence after her Iowa victory
Aug. 11: Romney gets heckled at the Iowa state fair
Aug. 13: Bachmann wins the Iowa straw poll
Aug. 13: Perry leaps into the race
Aug. 13: Paul finishes a close second in the Iowa straw poll
Aug. 13: Santorum places fourth in the Iowa straw poll
Aug. 14: Pawlenty drops out after placing third in the Iowa straw poll
Aug. 18: Cain announces his 9-9-9 tax plan
Aug. 18: Huntsman tweets, "I believe in evolution and trust scientists on global warming. Call me crazy." Conservatives are not pleased
Aug. 20: Gingrich travels to Hawaii to "campaign"--and to celebrate his wedding anniversary
Aug. 24: Perry takes the lead in national polls
Sept. 7: Gingrich scores when he scolds debate moderators in California
Sept. 12: Pawlenty endorses Romney
Sept. 12: At a Tampa debate, Perry faces criticism over immigration policy, the HPV vaccine and Social Security reform
Sept. 12: Bachmann blasts Perry for mandating the HPV vaccine and inaccurately suggests it could cause "mental retardation"
Sept. 22: At another Florida debate, Perry incoherently mangles an attack on Romney
Sept. 24: Cain wins Florida straw poll