WASHINGTON, June 23 (Reuters) - Republicans cheered after the U.S. Supreme Court on Thursday thwarted President Barack Obama's plan to offer millions of undocumented immigrants relief from deportation, but any sense of triumph might last only until the November presidential election.
If recent history is a guide, the stalled cause of immigration reform could energize Hispanic voters in support of likely Democratic nominee Hillary Clinton, hurting Republican Donald Trump's chances of reaching the White House.
Four years ago, Obama, seeking reelection to a second term, made Republican opposition to reform a central theme of his campaign. He ended up swamping his opponent, Mitt Romney, by almost a 3 to 1 margin among Latino voters, who now make up around 12 percent of the U.S. electorate.
Republican hopes for securing a larger share of that vote this election already seemed grim given Trump's vow to deport the estimated 11 million immigrants in the country illegally and to build a wall along the southern U.S. border.
Democrats were quick to assail the ruling and voice concern about the fate of the 4 million or so immigrants who were to be shielded from deportation by Obama's executive action. But it was also clear that they believe the high court has handed them a potent weapon to spur Latinos -- the fastest-growing segment of the U.S. electorate -- to vote in greater numbers.
The Latino voting bloc is expected to swell to 27.3 million in 2016, up 4 million from 4 years ago.
The prospect of Clinton filling the current vacancy on the top court with a liberal-leading justice who could, potentially, protect immigration-reform programs, may galvanize those voters as well. Republicans in Congress have refused to accept Obama's pick for the top court to fill the vacancy left by the death of conservative justice Antonin Scalia in February.
The justices' ruling on Thursday sent the question of the legality of Obama's program back to a Texas federal court for trial, leaving open the possibility that the matter could return to the high court on appeal at a later date.
The court's decision "just adds fuel to the fire that's already raging," said Brad Bannon, a Democratic strategist. "Each of these events raises the intensity and the Latino turnout even more."
In the wake of the ruling, immigration activists vowed payback in November's election and staged protests on Thursday.
FIRING UP LATINO VOTERS
A recent survey by Latino Decisions, a polling firm, showed that about half of the U.S. Hispanic electorate showed greater enthusiasm to vote in 2016 as compared to 2012, with support for Obama's pro-immigrant executive orders running high.
"We should expect similar dynamics this fall, perhaps even more so given the election is likely to determine the ideological direction of the Supreme Court," said David Damore, an analyst for the firm.
Given Trump's unpopularity with Latino voters, the question for many Democrats both in and outside the Clinton campaign has been less about attracting the bloc's support and more about making sure it votes in large enough numbers to help offset Trump's expected advantage among white voters.
The court's decision may also help make traditionally Republican states with increasing Hispanic populations such as Arizona more competitive this election, strategists in both parties said.
Reed Galen, a Republican strategist in California, said the ruling could boost Democratic hopes in Latino-heavy battleground states such as Nevada, Colorado, and Florida.
"The issue isn't getting [Latino voters] fired up," Galen said. "It's getting them to show up."
Galen believes there is little his party can do now to mitigate the damage he believes Trump has done to its appeal among Hispanics. A Republican National Committee "autopsy" report after Romney's defeat said it was essential for the party to broaden its appeal to Hispanic voters by embracing immigration reform.
"Trump has pushed the envelope on immigration so far for Republicans, I don't know this is going to be any more damaging," he said. "The barn's already been blown up."
But Rev. Samuel Rodriguez, the president of the National Hispanic Christian Leadership Conference, a conservative advocacy group, disagreed. He said Republicans in Congress could still enact reform this year, which would ward off Trump's deportation threat while building stronger ties with Latino voters.
"This is the quintessential green light for Republicans to put their money where their mouth is," Rodriguez said.
Many Republicans were careful on Thursday to applaud the court's ruling on the grounds that it curtailed what they viewed as an abuse of executive authority by Obama, without delving into the underlying immigration issues.
"The Constitution is clear: The president is not permitted to write laws -- only Congress is," said Paul Ryan, the speaker of the U.S. House of Representatives.
Ryan supports comprehensive immigration reform.
Trump, however, went further, praising the ruling and saying the election now held the key to blocking further illegal immigration.
"The election, and the Supreme Court appointments that come with it will decide whether or not we have a border and, hence, a country," he said in a statement. He has vowed to reverse Obama's executive actions on immigration as president.
(Reporting by James Oliphant; editing by Stuart Grudgings)