Hillary Clinton poses with students and faculty after speaking at Rancho High School on May 5, 2015 in Las Vegas, Nevada. Clinton said that any immigration reform would need to include a path to 'full and equal citizenship.'National Journal

The most important moment of Hillary Clinton's campaign so far came last week in Las Vegas, when she placed a huge strategic gamble this early in the race. Without much serious primary competition, she veered to the left of President Obama on immigration, pledging to legalize additional illegal immigrants and use executive orders to expand the scope of his measures. It's a telltale sign of how crucial the Hispanic vote is to her campaign, and how dependent she is on re-creating Obama's 2012 coalition to win.

That presents both an opportunity and a risk. Her decision to call out the Republican presidential field on the subject demonstrates how confident she is that, no matter how much certain GOP opponents run as centrists and appeal to Hispanic voters, no one will be able to outflank her on immigration reform. It was no coincidence that Jeb Bush and Marco Rubio, who are both hoping to make significant inroads with Hispanic voters as the GOP nominee, remained silent in the wake of her red-meat remarks. Without notable improvement on Mitt Romney's dismal 27 percent showing among Latinos in 2012, it's awfully tough to see a GOP path to the presidency. (Marco Rubio's pollster, Whit Ayres, has set the GOP's Hispanic benchmark in 2016 around 45 percent, though if black turnout levels decrease and/or Republicans make inroads with Asian-American voters, the magic number would be lower.)

At the same time, Clinton's move can be seen as a defensive maneuver, especially so early in the campaign. Maintaining Obama's overwhelming margins with Hispanic voters is something of a necessity for her to win the White House. She needs to figure out a way to excite the Hispanic base beyond what Obama's done, which is no small task. And that overreach reduces her prospects of making inroads with the white working-class vote, which abandoned Democrats en masse in the past two elections.

Clinton's stated support for citizenship towards illegal immigrants "with deep ties and contributions to our communities" goes beyond the Obama standard of those with family connections, and is bound to generate opposition among non-Hispanics. Obama deliberately avoided issuing any executive orders legalizing illegal immigrants during the 2014 midterm campaign because his advisers knew it was a major political loser. Clinton is going even further, with her team expressing unusual confidence that the country has taken a permanent progressive turn over the past several years. She will now need to offset the opposition by mobilizing Hispanics to show up to the polls and support her—even as their turnout rate has historically lagged well behind other demographic groups. She's giving herself little wiggle room to maneuver in the face of changed circumstances, such as the 2014 border crisis that raised fresh skepticism of immigration reform among the American public.

So while her move is based on the premise of a rising American electorate, it's also an implicit concession that she's unlikely to improve much on Obama's weak performance among white voters. And when you consider that even small GOP inroads with Latino voters could make a big difference— or unexpectedly lower turnout levels—Clinton doesn't have much of a choice but to pander to that constituency.

Put another way: Clinton is betting that it's easier to maintain Obama's 44-point margin of victory with Hispanics than it will be to improve by several points among white voters. That lesson was underscored in last year's midterms, when more-moderate Democratic Senate candidates in former Clinton strongholds, such as former Sen. Mark Pryor and Alison Lundergan Grimes, performed as poorly as Obama did.

This month's NBC/Wall Street Journal poll suggests that there's more potential for Republicans to pick off Hispanic voters than for Clinton to make inroads with whites. Against Bush, she receives 40 percent of the white vote (one point higher than Obama's total against Romney) and 66 percent of the Hispanic vote (five points behind Obama). Against Rubio, Clinton receives 41 percent of the white vote, but her support with Hispanics drops eight points from Obama's 2012 performance.

If those demographic combinations held, it still should be enough for Clinton to prevail, even as it's awfully close for comfort. But the bet on Hispanic voter preferences and enthusiasm to remain constant is awfully risky, given how volatile their voting record has been lately. It was just over a decade ago that George W. Bush carried 44 percent of the Hispanic vote in his reelection. In last year's midterm elections, when the fate of immigration reform was on the line, Hispanic voters stayed home and swung key races in Colorado and Nevada into GOP hands. A similar expectation that Obama's enthusiasm will translate to Clinton—and Latino population growth will automatically translate into a larger share of the electorate—is far from guaranteed.

"Many Hispanics don't embrace the political process. Half of them think the Democrats don't care about their community. These non-voters are very suspicious about most politicians," said David Damore, an analyst with the liberal-leaning polling firm Latino Decisions. "[Clinton] learned her lesson from 2008. She assumed that just because she has high name recognition with Hispanics, they're going to vote for you. They want to hear about their issues."

For good reason, the GOP's struggles with effective outreach among Hispanics—and the awkward dance in catering to the base on immigration while expanding the party's appeal—has been under the spotlight. But the flip side of the equation also presents a challenge for Democrats. Clinton needs to maintain overwhelming support and engagement from Hispanics—or risk giving Republicans a critical advantage. The fact that she feels the need to run to Obama's left on an issue her party should have in the bank is a warning that putting back together his winning coalition isn't as easy as advertised.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.