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John Quincy Adams, our greatest secretary of state (sorry, Hillary Clinton fans), thought that Cuba would inevitably become part of the United States. It hasn't, at least not yet, but two Cuban-Americans were serious presidential contenders this year.

Yes, neither Marco Rubio nor Ted Cruz won the Republican nomination, instead suspending their campaigns the nights they lost the Florida and Indiana primaries, respectively. But they did become Donald Trump's most serious competition. And if you imagine that a few things had happened a bit differently, you might plausibly believe that one of them would now be mulling his VP pick and preparing an acceptance speech for Cleveland.

Rubio, born May 1971, and Cruz, born December 1970, are young for presidential contenders. Neither was eligible to vote for Ronald Reagan or George Bush in the 1980s. Rubio was a college senior and Cruz a first-year law student when Bill and Hillary Clinton entered the White House in January 1993.

Neither was a national figure when Barack Obama was elected in 2008. Rubio was ending a two-year term as speaker of the Florida House of Representatives. Cruz was serving as solicitor general of Texas, appointed by Attorney General (now Governor) Greg Abbott.

Donald Trump was flirting with the idea of running for president in the 1990s, two decades ago. Just about no one eight years ago imagined that Rubio or Cruz would be serious candidates this year.

Yet for those who follow politicians closely there were signs. Rubio's farewell speech to the Florida House, recounting how the son of an immigrant bartender could rise in America, got rave reviews on conservative websites.

Cruz, though unable to leverage his Bush campaign experience to a White House job, was cultivating conservative legal and political insiders. I remember him asking me whether he should run for attorney general of Texas if Abbott ran for governor in 2012. (I said it was up to him; the eventuality did not arise.)

These were signs that both men had serious political ambitions, but so do many young men and women. And neither had much in the way of institutional or establishment support when he challenged a leading politician for a Senate seat in the Obama administration years.

Rubio's initial opponent for the Senate in 2010 was the incumbent Republican governor of Florida, Charlie Crist. When others backed out of the race, Rubio stayed in and got endorsements from county Republican organizations dismayed by Crist's liberal policies and (literal) embrace of Barack Obama on a 2009 Florida visit.

Crist withdrew from the Republican race and ran as an Independent. That meant that Rubio won easily in the Republican primary and in a three-way general election.

In the 2012 Texas open-seat Senate contest, Cruz challenged the wealthy lieutenant governor of Texas, David Dewhurst, whom most officeholders, including Gov. Rick Perry, supported. Cruz ran a strong second in the initial primary, won the runoff and coasted to a party-line victory in November.

As young senators from the third- and second-largest states, Rubio and Cruz could have settled in for long legislative careers. Instead both set their sights higher, and suffered setbacks. Rubio's co-sponsorship of the Gang of Eights immigration bill was rejected by most Republicans and hurt him in 2016. Cruz's call to repeal Obamacare by threatening government shutdown antagonized Republican leaders and Senate colleagues.

Nevertheless, their skill sets served them well in the presidential race. Rubio's combination of shoutouts to cultural conservatives and emollient attitude toward those who disagree helped him win votes from the religious right and upscale suburbanites. Cruz's stentorian style and claims of adherence to conservative principles gave him strong support from "very conservative" voters.

In different ways, both shined in debate, with only a few lapses. Both ran well-organized campaigns, with Rubio rounding up endorsements and Cruz building the race's most disciplined and rigorous organization.

Both also attracted attacks, and not only from Donald Trump. Rubio was the target of attack ads from Jeb Bush's super PAC and a debate ambush by the flailing Chris Christie. The latter allowed John Kasich to finish second in New Hampshire with only 16 percent of the vote and to stay in the race siphoning off upscale voters from Rubio.

Now, defeated by Donald Trump, both their careers seem in tatters. Rubio is leaving the Senate and Cruz has close to 99 enemies there. The lesson: Ambition and talent can take a politician a long way up -- and down.