Immigration politics has long offered great promise but also threatened great peril for Republican presidential hopeful Marco Rubio.
The heated fight over what to do about people in the country illegally poses a dilemma for the son of Cuban immigrants: How far can Rubio go in appealing to the party's core of conservative white voters before he undercuts his potential to win the general election?
The Florida senator vowed this month to terminate the Obama administration program that offers a reprieve from deportation to thousands of immigrants brought to the U.S. illegally as children. He has played down his leading role in pushing for a bill to offer a path to citizenship to millions of immigrants in the country illegally.
He also has largely avoided confrontation with real estate mogul Donald Trump, who has called for mass deportations, a wall on the Mexican border and an end to birthright citizenship. Two other Republicans, Ohio Gov. John Kasich and former Florida Gov. Jeb Bush, have denounced Trump's agenda more forcefully.
Rubio is facing pressure on the right not just from Trump, who branded him the "king of amnesty" on Friday, but also from Ted Cruz. The senator from Texas has accused Rubio of joining Obama in pushing for "a massive amnesty plan."
One of the rationales for Rubio's candidacy was that he would broaden the base for the GOP with his presumed appeal to minority voters, especially Latinos.
But the Republican field's tough talk about illegal immigration, mostly instigated by Trump, risks alienating those voters, especially in the Southwest, where the growing Latino populations of two swing states, Colorado and Nevada, can decide a close presidential election. It also spells trouble in Florida, another battleground where Latinos twice backed President Obama by lopsided margins.
Josh Penry, who leads Rubio's Colorado campaign, recalled that Mitt Romney took a hard line on illegal immigration in the 2012 Republican primaries, then won less than a quarter of the state's Latinos in the general election.
"It cost him profoundly," Penry said in an interview at a coffeehouse in Denver's Cherry Creek area.
Rubio, however, would be the nation's first Latino president, and his heritage could help offset any backlash from the primaries. His campaign manager, Terry Sullivan, said the Spanish-speaking senator's upbringing in an immigrant household would appeal to Latinos, regardless of his approach to illegal immigration.
"Because he can connect to that, and because he so embodies that, that resonates with them," Sullivan said.
After Romney's rout in 2012, Rubio led the Republican Party's drive to mend its tattered relations with Latinos, co-authoring the bipartisan bill that included the path to citizenship.
Soon after it passed the Senate in 2013, Rubio abandoned the bill, saying border security must be tightened before Congress takes action on the status of 11 million immigrants in the country illegally. That reversal has damaged Rubio's standing among Latinos, said Bob Martinez, a former Colorado Republican chairman unaligned in the party nomination fight.
"The fact that Rubio backed off the immigration reform bill is just not good," said Martinez, who sees the 44-year-old Rubio's youth and speaking skills as good qualities but believes Republicans' seething rhetoric on immigration has harmed the party's effort to regain the White House.
Penry, a former state lawmaker who is building a county-by-county network of Rubio backers in Colorado, hopes Latinos will give the senator credit for trying to "drive solutions" on illegal immigration. In a closely divided state where personality and character can swing elections, Penry said that Rubio would strike Latinos as a charismatic young champion of the middle class.
"He's just not a scowling, finger-wagging, crusty old white dude," Penry said.
Antonio Gonzalez, the president of Southwest Voter Registration Education Project, said Rubio's sometimes charming personality could make him a tough rival for Clinton in states like Colorado, where she already faces a formidable challenge matching the heavy voter turnout that Obama inspired.
At the same time, Rubio "hasn't done himself any favors with his playing all the angles on immigration," Gonzalez said.
Southwest Voter and other groups are tapping a backlash against Trump to try to sign up thousands of new Latino voters in Colorado, Nevada and other states. In Colorado, more than 200,000 eligible to vote next year remain unregistered.
Across the Southwest, rapid growth of the relatively young Latino population has enhanced their clout. Latinos' share of the presidential vote in Colorado grew from 8% in 2004 to 14% in 2012.
Former Denver Mayor Federico Peña, a Democrat, said Rubio's failure to stand up to Trump would ultimately hurt him.
"Fundamentally, he doesn't represent the interests of Latinos in this state or anywhere," said Peña, who led a rally outside the GOP presidential debate in Boulder last month to assail the candidates on immigration and launch a Latino voter registration drive.
A few weeks later at a Clinton campaign house party in the Denver suburb of Aurora, senior Clinton advisor Karen Finney echoed that argument.
"The contrast could not be sharper," Finney said of Rubio and Clinton. "She is very much for a path to legal citizenship, believing that anything less than that creates second-class status."
The rising number of Latino voters means that Rubio would need to do far better than previous Republican presidential candidates among Colorado Latinos, said Joelle Martinez, executive director of the University of Denver's Latino Leadership Institute. Ethnic solidarity could help him.
"Marco Rubio can absolutely change the game in the Southwest if he's the nominee," she said, "but if — and only if — he's serious about comprehensive immigration reform."
Finnegan reported from Denver; Lee from Los Angeles.