Trump is proposing more sweeping change than the 1996 platform Dole repudiated.

The businessman argues that the 14th amendment does not, in fact, guarantee citizenship to the estimated 4.5 million U.S. born children of undocumented immigrants; if the courts agreed, that presumably would make those children subject to the deportation he pledges to pursue against all those here illegally.

But in responding to Trump, the 2016 Republicans have wavered far more than Dole did. About half of the GOP field (including Ted Cruz, Rick Santorum, and Ben Carson) has also endorsed ending birthright citizenship, at least prospectively. Scott Walker quickly embraced the idea before backpedaling to reject it. Even the two candidates that most forthrightly rejected Trump’s call could not completely escape his gravitational pull.

Marco Rubio said he would not seek to change the constitution, but would take unspecified steps to combat those “taking advantage of the 14th amendment.” Jeb Bush, while also rejecting constitutional change and praising America’s “diversity,” courted Trump’s constituency by adopting his incendiary “anchor babies” language.

This rightward lurch – behind an almost certainly hopeless cause of constitutional change – captures the core GOP dilemma now unfolding in the party’s nomination contest.

The Republican electoral coalition now relies on preponderant majorities from the groups most unsettled by demographic and cultural change: older, non-college and rural whites. There are no longer enough of those voters to guarantee Republicans a national majority: that’s why Democrats have won the popular vote in five of the past six presidential elections. Yet, as Trump’s rise shows, many of those voters militantly oppose the policies (like immigration reform) that might help the party expand its coalition.

By demonstrating that dynamic so viscerally, Trump’s ascent has further weakened the Republicans who contend the party must bend to, rather than resist, demographic change.

After Mitt Romney lost decisively in 2012 despite winning a greater share of white voters than Ronald Reagan did in 1980, the Republican National Committee’s official post-election review concluded the party “will lose future elections” without attracting a larger share of the growing minority vote. That impulse peaked in June 2013, when 14 Senate Republicans (led by Rubio and 2008 nominee John McCain) helped pass sweeping immigration reform that included a pathway to citizenship for undocumented immigrants.

But with conservatives in revolt, the GOP current has since reversed. The House refused to consider the Senate bill, and instead repeatedly passed legislation to block President Obama’s executive orders providing legal status for some of the undocumented. Most Republican-led states sued to stop Obama’s executive action as well. Rubio repudiated his own bill. Now the 2016 Republican contenders are collectively offering an even harsher approach on immigration than Romney did when he embraced the “self-deportation” policy that discredited him with many Latinos and Asian Americans.