WASHINGTON — South Carolina Republican Sen. Lindsey Graham, one of the bipartisan Gang of Eight seeking historic reform of American immigration policy, has warned his party colleagues they’d better get aboard or forget about electing one of their own to the Oval Office in 2016.

While predicting the eventual bill will get more than 70 votes in the Senate, Graham said the Republican Party is “in a demographic death spiral” after having lost more than 70 percent of the Hispanic vote in the 2012 presidential election. He argued that the main reason was its opposition to immigration reform urged widely among Latino voters.

One prominent member of the gang, Republican Sen. Marco Rubio of Florida, a prospective 2016 presidential candidate, has been a leading figure in the reform negotiations, pushing for a path to American citizenship for Hispanics in the country in conjunction with stronger security along the Mexican border.

But a political hangover from the 2012 campaign, in which GOP standard-bearer Mitt Romney became a target of Latino activists for clinging to what was inartfully referred to as “self-deportation,” still hovers over the debate. That is, the notion that illegal aliens residing here would have to return to their country of origin and get to the back of the line of applicants for legal entry and eventual citizenship.

Graham insisted on Sunday’s Meet the Press on NBC that “if we don’t pass immigration reform, if we don’t get it off the table in a reasonable, practical way, it doesn’t matter who you run in 2016.” He went on: “And the only way we can get back in good graces with the Hispanic community in my view is (to) pass comprehensive immigration reform. If you don’t do that, it really doesn’t matter who we run.”

That assessment is a reasonable one, but it seems to suggest that enactment of a more dependable gateway to citizenship for Hispanics already here and their family members will in itself throw open the floodgates to millions of such ethnic voters ready and eager to vote Republican.

More probable is that such immigration reform will only enlarge the pool of Latinos voting Democratic, based on past patterns and the general damage to the Republican brand by the eight years of the George W. Bush presidency and the hapless Romney campaign of 2012.

The junior George Bush won the 2000 Republican presidential nomination with strong Latino support as governor of Texas, having advocated policies that held promise of much greater progress on the national level. Those promises went largely unrealized, and the increasingly unpopular war policies that eroded Bush’s support among the general electorate in his second term also took their toll among Hispanics.

Then came the 2012 presidential campaign, in which the Republican Party stumbled through a marathon of primaries that only underscored its internal divisions. In order to secure the party’s nomination, Romney was obliged to sound more conservative than his previous record as governor of Massachusetts had suggested.

Graham’s warning of a Republican death spiral was an unusually harsh appraisal from a loyal party member. It could be dismissed as an overzealous shot across the bow of fellow Republicans to get behind the immigration reform, for which he has worked long and hard. At the same time, he predicted a political breakthrough in its passage, which smacks of putting all of the party’s eggs in that one basket.

Graham said he thought former Florida Gov. Jeb Bush would have a good chance of winning if he were to run for president in 2016. Doing so likely would help with the Hispanic vote, inasmuch as his wife is a Latina, he is fluent in Spanish and he built a pro-Hispanic record in Tallahassee. But this Bush’s stronger suit may be his comparably more moderate and congenial posture than that of his brother George.

In any event, it’s notable that Graham has put the issue of immigration reform in uncommonly cataclysmic terms for his party, after it bet all in 2012 on getting rid of Obama and Obamacare as the ticket to returning to power — and lost.

(Jules Witcover’s latest book is Joe Biden: A Life of Trial and Redemption (William Morrow). You can respond to this column at juleswitcover@comcast.net.)

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