Denver - They'll praise him, invoke his legacy and summon his blessing on their quest to hold the White House.

    But as Republicans gather at their national convention in St. Paul, Minn., to nominate Sen. John McCain, they face the prospect that the era of Ronald Reagan is ending after dominating their party and American politics for nearly three decades.

    The winning coalition that Reagan built of economic, foreign policy and social conservatives is splintered. The issues he used to define the party have changed. And the national rejection of an unpopular president - Jimmy Carter - helped Reagan launch a political revolution but now benefits the other party as Democrats rally against the legacy of George W. Bush.

    "It doesn't look good at all," said Frank Luntz, a Republican strategist who helped the party seize control of the House of Representatives in 1994. "They can't recreate the Reagan coalition. Life has changed. America's priorities are different."

    Indeed, 2008 could punctuate a turning point in the way that Americans view the role of government - a shift potentially as significant as those that ushered in rise of big-government liberalism in 1932 and the turn to modern conservatism and skepticism about government in 1980.

    Now, after a decade in which Republicans increasingly embraced a more activist government, the party is facing a pivotal decision about what it thinks about big government - for it, against it, or what Lee Edwards called "something in between."

    "Americans are still small 'c' conservative. That may be changing in regard to the Republican Party," said Edwards, a scholar at the Heritage Foundation, a conservative think tank.

    In the recent Republican primaries, he said, "there was a lot of lip service paid to Ronald Reagan by the candidates. But when you get down to specifics, they are tilting away from Reagan toward some new mix."

    Times have changed, and the issues that bound the Reagan coalition together have changed.

    The unifying threat of the Soviet Union is gone. The federal government's highest tax rates no longer top 50 percent. Welfare has been reformed to require work.

    The new political environment pulls at some of the core principles of conservatism that have defined the party since Reagan.

    On national security, for example, "neoconservatives" push for an interventionist foreign policy and nation building in places such as Iraq. Others push for warrantless spying on U.S. citizens, alarming the civil-libertarian wing, which is skeptical if not hostile to unabridged government power.

    On social policy, religious conservatives want an aggressive government to regulate marriage, traditionally an issue left to the states.

    And on fiscal policy, Republicans have increased the size and cost of the federal government and its debt. Domestic spending grew much faster under President Bush and a Republican Congress than it did when Democrat Bill Clinton was in the White House.

    "The coalition that elected Reagan is no longer there," said William Lacy, a political director in the Reagan White House and now director of the Robert J. Dole Institute of Politics at the University of Kansas.

    "Neocons are willing to throw out some of the principles of conservatism," said Lacy, who briefly managed former Tennessee Sen. Fred Thompson's presidential campaign.

    "Christian conservatives are more demanding in tactics and goals than they were. What they've done is take conservatism from being a federalist approach with focus on liberty and make it a big-government style of conservatism using the federal government to dictate what people do."

    Some of what melted the glue of the coalition simply is rooted in personality.

    Reagan was a masterful politician whose personality and communication skills allowed him to hold together rival factions in a big-tent party. His intolerance for public fights in the party was so well known it became known as the 11th commandment: speak no ill of a fellow Republican.

    "It's a very rare leader who can bring together disparate groups when they agree on 70 percent and disagree on 30 percent. Reagan was able to succeed at that. Bush has been much more typical, more susceptible to these divisions," Luntz said.

    But more than that, new power centers such as talk radio and the Christian right now openly enforce ideological litmus tests and aggravate divisions. "People now are looking for reasons to argue rather than reasons to cooperate," Luntz said.

    Indeed, one of the most frequent targets of criticism within the party has been none other than the man they're about to nominate, McCain.

    Should McCain go on to win the White House, he could redefine the party - perhaps tougher on federal spending, more protective of civil liberties at home - yet also remain suspect to many conservatives for such stands as advocating limits on political speech as part of campaign-finance law.

    If he should lose, a party that likes to go to the next guy in line will have no heir apparent and likely will break into the kind of hot debate that it saw in the political wilderness years of the mid-1960s.

    That era saw Barry Goldwater and Reagan plant the seeds for a conservative ascendance - but one that wouldn't take hold until after moderates Richard Nixon and Gerald Ford had been president.

    "There are big elements still out there waiting for someone to unite them," Lacy said.

    But that won't happen in 2008, Luntz said. Even if McCain wins, he said, it will be because voters reject Democrat Barack Obama, not because McCain was able to forge a new Republican coalition.

    Said Lacy: "We don't really know what we've got."