1. The announcement

Many Republicans were unsure Trump would even run, given his past flirtations with White House bids that didn’t materialize. But his nationally televised announcement — taking the escalator in the lobby of Trump Tower — galvanized many GOP voters. However, his remarks about Mexican immigrants — they they were “bringing crime” and were “rapists” — would spark the sort of controversy that would become synonymous with Trump’s candidacy.

2. Early rise

Despite perceived mistakes — from his announcement speech to his criticism of John McCain's war record in July — Trump quickly surged to the front of the crowded GOP field. The McCain comments in particularly, where he said the Arizona senator and decorated Vietnam prisoner of war was a war hero only “because he was captured,” likely would’ve doomed other candidates. But Trump’s rise in the polls following the uproar would be an early sign of his immunity to the forces that would bring down other political figures.

3. The first debate

The Aug. 6 debate would soon be known more for a long-running feud he would form with moderator Megyn Kelly of Fox News. She asked him about past derogatory remarks he’d made about women at the debate’s start, resulting in a controversial response the next night in an interview with Trump in which he suggested she had “blood coming out of her wherever” during the exchange. Despite the tiff, though, Trump’s first-ever debate earned good reviews among his partisans and proved his summer surge was more lasting than his rivals may had hoped.

4. Terror responses

Donald Trump speaks during a rally in Mt. Pleasant, S.C., on Dec. 7, 2015. (Photo: Mic Smith, AP)
Trump’s call to impose a temporary ban on Muslims entering the United States following the San Bernardino terror attack in December, which came the month after the Islamic State strike in Paris, strengthened his hand with Republican voters. However, the provocative proposal would raise long-lasting concerns about his electability among many Republican leaders.

5. Iowa caucuses

Polls showed Trump poised to capture the opening Iowa caucuses, but in his first test before voters, the real estate mogul suffered a temporary setback. Despite a fairly close second-place finish, Ted Cruz's victory dented Trump's aura of inevitability. Meanwhile, the win propelled Cruz forward and elevated him as Trump’s top challenger for the GOP nomination.

6. New Hampshire primary

Trump rallied from his Iowa loss to a double-digit win in the nation's first primary. It would be Trump’s first electoral victory, and it re-established him as the undisputed candidate to beat in the GOP race.

7. South Carolina primary

In a state that’s long been key to capturing the Republican nomination, Trump won again by double digits, illustrating his appeal in the South and among evangelicals, which would be key to his later success during the Southern-focused March 1 Super Tuesday primaries. An added bonus, from Trump’s perspective: After his distant fourth-place finish here, former Florida governor Jeb Bush would end his presidential campaign. The son and brother of former GOP presidents who was one of Trump’s main antagonists had been an early front-runner in the GOP race.

8. Florida primary

Marco Rubio emerged as the last, best hope of the so-called Republican establishment after the opening primaries, securing the support of a wide array of GOP office-holders despite few early successes in the primary. Rubio’s campaign rested on winning his home state of Florida, which would award all of its 99 delegates to the contest winner. However, Trump would knock out another potential threat, capturing the Sunshine State by nearly 20 points.

9. Wisconsin primary

n a setback for Trump, Cruz won won Wisconsin easily at a time when Never Trump forces were organizing. Talk of a "contested convention" dominated the airwaves, as many thought Trump would be unable to secure the 1,237 delegates needed to secure the nomination prior to the July Cleveland convention. However, Wisconsin, in many ways, proved to be the high-water mark for Cruz, as two weeks later, Trump would score a decisive win in delegate-rich New York, winning with 60% of the vote and erasing many concerns that he had a ceiling of support among GOP voters.

10. Indiana and the end

After a string of wins in the Northeast, Trump wrapped up the race by winning this conservative state in early May, forcing Cruz from the race that night and Ohio Gov. John Kasich the next day. Later in the month, he would hit the magic number needed to guarantee his nomination at the party gathering in July, capping an improbable political rise.