Julian Castro's keynote speech at the 2012 Democratic National Convention was a potential star-making appearance designed in part to catapult the emerging politician to greatness.

The former San Antonio mayor was widely mentioned as a can't-miss prospect who would lead Texas Democrats to a historic statewide victory as a 2018 candidate for governor. Others saw him as a presidential contender, particularly after he was considered as a running mate for Hillary Clinton in 2016.

Yet, in the years since his keynote speech in Charlotte, N.C., Castro has been content to remain on the sidelines as other Democrats moved ahead of him in attention and popularity.

Castro's dreams, he hopes, won't be deferred much longer.

In his hometown San Antonio on Saturday, Castro is launching his campaign for president, hoping to outrun a potential large and diverse field of Democratic Party contenders. If successful, he would be the first Hispanic and one of the youngest Americans to win the White House.

It won't be easy.

Since 2012, potential candidates like Sens. Elizabeth Warren of Massachusetts, Kamala Harris of California and Cory Booker of New Jersey have moved ahead of Castro in name recognition. And former Vice President Joe Biden and Vermont Sen. Bernie Sanders, the 2016 runner-up to Hillary Clinton for the Democratic Party nomination for president, have far greater standing with voters than Castro.

Perhaps more disturbing for Castro are the Lone Star rumblings that former U.S. Rep. Beto O'Rourke, now the most popular Democrat in Texas, is seriously considering a campaign for president.

Still, with progressive Democrats urging that the party try something different in its rematch against the Republicans and President Donald Trump, Castro — with a few breaks and hard work — could make a strong run.

"There's not a clear road for him right away to the top tier," said Dante Scala, a political scientist at the University of New Hampshire. "His burden is to show that it's his time, right now, and not in another four years or another eight years."

Democratic Rep. Colin Allred of Dallas, who served under Castro in the U.S. Department of Housing and Urban Development, said the former HUD secretary is a strong presidential candidate.

"As the former mayor of the fifth-largest city in the country and cabinet secretary, there is no doubt in my mind that Secretary Castro has the right temperament and experience to be president of the United States," Allred said. "Perhaps now more than ever our country needs someone who will unite us around our common dreams instead of dividing us or stoking fears."

From local politics to national stardom

Castro was born into a well-known activist family.

His mother, Rosie Castro, is a 1970s leader of La Raza Unida, the radical Texas movement that pushed a strong Chicano identity and promoted civil rights for Mexican-Americans. He is the identical, older twin brother of Rep. Joaquin Castro, who also is a former state representative.

He's married to elementary school teacher Erica Lira Castro and they have two children.

A lawyer by trade, Castro, 44, caught the eye of former President Barack Obama and others during his tenure as San Antonio mayor. He served the city from 2009 to 2014 and was known as a bridge-builder who managed to convince residents and business leaders to back a $30 million sales tax proposal to fund pre-kindergarten education. In 2010, Time magazine named him as one of the "40 under 40" rising American political stars. Before his term as mayor, Castro, at age 26, was the youngest person elected to the San Antonio city council.

National Democrats, looking to develop young Hispanic leaders and make inroads in that critical election demographic, began mentioning Castro as a budding star.

Julian Castro, former U.S. Secretary of Housing and Urban Development, speaks during the Texas Democratic Convention on June 22, 2018, at the Fort Worth Convention Center in Fort Worth. (Ashley Landis / Staff Photographer)

When he was picked to make the 2012 keynote address at the Democratic National Convention, it was hoped that the address would launch his national career, much like it did Obama's when he delivered the address at the 2004 convention for Democratic Party nominee John Kerry, the former Massachusetts senator.

While praised in some quarters, Castro's speech didn't propel him to stardom as Obama's did eight years earlier.

Still, years later Obama took steps to boost Castro, appointing him HUD secretary, and the youngest member of the president's Cabinet.

With momentum from that appointment, Castro in 2016 was mentioned as a potential vice presidential candidate, though Clinton settled on Virginia Sen. Tim Kaine.

Castro continued at HUD until Obama left office in 2017.

With the 2018 midterm elections approaching, he was at a crossroads. Should he run for governor, as many expected, or wait for another opportunity?

Governor's mansion or White House?

He was courted and virtually expected to run for governor against Republican incumbent Greg Abbott in 2018. But he never publicly explored such a run, and the Democrats' frantic search for an attractive candidate ended with former Dallas County Sheriff Lupe Valdez, whom Abbott easily defeated to win a second term.

With his HUD experience in tow, Castro instead set his sights on running for president, visiting early primary states like Iowa and New Hampshire, where he'll be next week.

His problem, however, is that HUD was not a high-profile position in Obama's administration. And when the nation's first black president left office, Castro disappeared from the headlines.

His decision to sit out the 2018 Texas elections could also be problematic. As he watched, O'Rourke undertook an underdog Senate campaign against Ted Cruz that captured the attention of the nation and brought Democrats within 2.6 percentage points of their first statewide victory since 1994.

Mike Collier, candidate for Texas lieutenant governor, greeted Julian Castro, former secretary of Housing and Urban Development, during the Texas Democratic Convention on June 22, 2018, at the Fort Worth Convention Center in Fort Worth. (Ashley Landis / Staff Photographer)

Suddenly O'Rourke, not Castro, became the Texan most mentioned as the champion Democrats needed to face off against Trump.

If O'Rourke decides to enter the race, it could mean that Castro would have a hard time wrestling the delegate-rich state of Texas, where Democrats were consumed by Betomania.

"Because of all the attention O'Rourke has gotten after his Senate campaign, he's in line to be the 'it' candidate," said University of Iowa political scientist Timothy Hagle. "That's one of the obstacles Castro is facing."

Scala, the New Hampshire political scientist, agreed.

"It's hard for him to be rated No. 1 in his home state," he said.

So how does Castro gain footing in a tough slog?

In the past, analysts like former George W. Bush adviser Mark McKinnon have said Castro could be the first Hispanic American elected president. But that was in 2010.

Analysts say he'll have to immerse himself in Iowa, New Hampshire or both to get a strong showing in the early primary contests. That would set him up for the March 5 Super Tuesday showdown that includes Texas, California and other large states.

"This is an exciting time in Texas, with new and authentically Texas voices, like Secretary Castro, stepping up to lead," Allred said.

But even then he could have to outduel fellow Texan O'Rourke, as well as Harris or other Californians who might get into the contest and use Super Tuesday as a launching pad.

"He's too young to say that things have passed him by," Scala said. "The challenge is that it's likely to be a crowded field. How does he make it to the front of the pack?"