A former punk-rocker who needed a hefty upset to win his congressional seat six years ago will have to pull off an even bigger one to unseat powerful Sen. Ted Cruz.

Beto O'Rourke, a 44-year-old Democrat from the remote West Texas city of El Paso, has advocated for legalizing marijuana and preaches tolerance on the U.S.-Mexico border in defiance of President Donald Trump's "Build that wall" mantra.

On Friday, O'Rourke should formally announce his 2018 Senate candidacy against Cruz, a conservative who finished second to Trump in last year's GOP presidential primary.

The third-term congressman and fluent Spanish speaker is the kind of rising political star Democrats hope can help begin turning deep red Texas blue, aided by a booming Hispanic population and state politics pushed even farther right by Trump and Cruz. He first made a name for himself playing guitar for Foss, an El Paso punk rock band that included drummer Cedric Bixler-Zavala, who went on to play for the Grammy Award-winning act The Mars Volta.

But before O'Rourke can challenge Cruz, he'll have to emerge from a Democratic primary field that could include another up-and-comer, fellow Rep. Joaquin Castro from San Antonio.

"The Trump factor. He's the gift that keeps on giving to Democrats in Texas," said the state's Democratic Party Chairman Gilberto Hinojosa. "It's energizing the base and changing the whole dynamics of electoral politics here, and that's what these two guys see."

It's hard to imagine any Democrat taking Texas by storm, much less toppling Cruz, who added to his national stature running for president while remaining popular in most GOP circles back home. A Democrat hasn't won statewide office in Texas in 23 years, the nation's longest losing streak by a political party.

Still, O'Rourke insists Cruz is beatable and there are some positive signs for Democrats, who in November swept down-ballot races in Harris County, which includes Houston, and made notable gains in other fast-growing areas. Trump still beat Hillary Clinton in Texas by 9 percentage points -- but that was the first time a Republican didn't carry the state by double digits since 1996.

Castro hasn't tamped down speculation he too will run for Senate and would be favored over O'Rourke. Both have crisscrossed the state, engaging top donors and party activists. Hinojosa says he's assuming Castro will run with help from his twin brother, Julian, the former San Antonio mayor who was President Barack Obama's Housing and Urban Development Secretary.

On resume alone, O'Roruke would seem an unlikely choice, but he has been an underdog before.

O'Rourke was elected to the El Paso City Council at age 32 but remained virtually unknown outside his hometown until the 2012 Democratic primary, when he ousted eight-term Rep. Silvestre Reyes, a former House Intelligence chairman.

His El Paso district is strongly Democratic, making general elections since then an afterthought. The dynamics will be far different in a Senate race: Even if O'Rourke survives a dogfight primary, beating Cruz would be far tougher.

"I think his history indicates if he decides to do this, he will spend all his energy, time and resources on getting elected," said Jose Rodriguez, a state senator from El Paso who has hosted past O'Rourke congressional fundraisers. "There are indicators that people are tired of what's going on with the current administration (and) the kind of campaign that Ted Cruz ran."

O'Rourke has long been a supporter of legalizing pot to slow the drug war that for years turned Ciudad Juarez, across the border from El Paso, into one of the world's deadliest places. He authored the 2011 book, "Dealing Death and Drugs," which argued that America's war on drugs had failed.

O'Rourke was arrested in 1995 for breaking and entering after jumping a fence at the University of Texas at El Paso during what he now says was a prank, but prosecutors declined the case. Three years later, O'Rourke was arrested for drunken driving and received deferred adjudication to avoid conviction, an incident he has called a mistake.

His father was a former El Paso County judge and a longtime Democrat who switched parties in 1996 to run unsuccessfully for Congress as a Republican. The younger O'Rourke is an outspoken advocate for bipartisanship, saying both parties should work together to foment trade and cultural exchange on the border.

When a snowstorm canceled flights into Washington this month, O'Rourke and Republican Rep. Will Hurd, from a sprawling Texas district next to his, spent 36 hours driving a rented Chevy Impala from San Antonio to the nation's capital, livestreaming much of the way. The pair became an internet sensation during hours of listening to Johnny Cash, hitting Whataburger and jointly opposing Trump's border wall.

There was widespread speculation Cruz could face a GOP primary challenge for being slow to endorse Trump last fall -- but much of that has faded since Cruz has become a vocal supporter of Trump after November. Cruz spokeswoman Catherine Frazier declined to comment on O'Rourke's entering the 2018 Senate race.

Perhaps tellingly, Cruz has sometimes singled out the Castro brothers for past criticism. He hasn't targeted O'Rourke, at least not yet.