Movement conservatives and self-styled Republican populists have long been joined in conflict with the party establishment, but the GOP presidential race has set them on a collision course.

Friction between these two GOP factions is being fueled by the increasingly bitter battle between Sen. Ted Cruz of Texas and New York celebrity businessman Donald Trump in the race for the Republican presidential nomination. Cruz represents ideologically committed conservatives, although he has appealed with some success to populist voters. Trump has given big government populists, who have aligned with the GOP mostly for cultural reasons, a champion, while appealing to some movement conservatives.

"Many movement conservatives are frustrated about Trump's rise," a conservative political operative who works in the nation's capital told the Washington Examiner, requesting anonymity in order to speak candidly. "It's hard to look at Trump's history and come to the conclusion that he's a conservative."

The conservative-populist alliance has been built around a shared distrust of, and frustration with, what both camps view as the entrenched and out of touch Republican Party leadership in Washington. To these voters, and the collection of advocacy groups that claim to speak for them in D.C., that includes members of Congress (rank-and-file, as well as leaders,) the national party committees, and the community of professional political consultants and K Street lobbyists.

Conservatives and populists largely agree on illegal immigration — that it must be stopped and that elected Republicans haven't done anything about it. They passionately oppose President Obama and his signature health care law, are conservative on social issues and in broad agreement that the government should butt out of their lives. And, they have made common cause generally over their belief that elites in New York and Washington have rigged politics and the economy to their advantage.

But after that, these two GOP voting blocs tend to part company.

Movement conservatives favor smaller government and reducing taxes for all income levels, free trade and ending industry-specific tax breaks — derided as "crony capitalism," and a major overhaul of entitlement programs like Medicare and Social Security to reduce projected long-term deficit spending. Populists are suspicious of entitlement reform, wary of free trade agreements, open to hikes in taxes and the minimum wage and fine with industry tax breaks — at least if they protect local jobs.

For doctrinaire conservatives and their allied groups, these differences haven't matter much, because only they satisfied the populists' desire to vote against the so-called Republican establishment. But Trump's command of the Republican primary campaign has given them an alternative that better matches their worldview. Tea Party heroine Sarah Palin's endorsement of Trump made plain this week just how stark their differences are on key issues, and how fragile their political marriage really is.

A conservative strategist who has advised insurgent Republican candidates said these differences have often been apparent in the South, the bedrock of the Republican Party's electoral support. "Mississippi is a pretty pro-life, Republican state," this operative said. "But they like getting stuff from the government. It's why there's been less support for the types of candidates backed by conservative outside groups, there and in Alabama — even though they're heavily Republican — than in Ohio, Georgia and Texas."

The populist wing of the GOP tends to be white, working class and economically and culturally disaffected. They either attended some or no college, although they also include the college educated. Many were, or might have been Democrats, had the Democratic Party, in their view, not abandoned them by placing a greater value on catering to the desires of ethnic minorities and immigrants. They describe themselves as "conservative."

Usually, these voters lock hands with doctrinaire, small government conservatives to form a firewall through which a Republican primary candidate has trouble passing unless they meet the minimum threshold of conservatism demanded by the conservative wing of the GOP. But Trump, because of his appeal to populist voters, is upending that deal, and in doing so usurping power from the conservative wing, although many political analysts believe this dynamic will be short-lived.

To outflank Cruz in Iowa, he is vowing to keep the gravy train for ethanol subsidies rolling (Cruz supports sun-setting federal subsidies over five years, beginning in 2017. Washington's investment in Iowa corn crops is an important part of the Hawkeye State economy. Trump opposes entitlement reform and doesn't talk about reducing the size and scope of government, just managing it better.

Political analyst Ronald Brownstein, who writes for National Journal, describes Trump's impact in the Republican primary this way: "The blue-col­lar wing of the Republican primary electorate has consolidated around one candidate." This works for Trump as long as college educated, white collar Republicans split their vote among Cruz and a host of Republican contenders that are labeled as establishment even if the moniker is an unfair representation of their record.

The fight for votes in Iowa by Cruz and Trump is temporarily obscuring the longstanding internecine war going on between the governing and insurgent wings of the GOP. But some veteran Republican operatives can't help but chuckle at the predicament conservatives find themselves in. They have spent years accusing so-called establishment Republicans of being insufficiently conservative. Now, they're facing similar charges of heresy from the populist wing.

"If 'conservative populist' means a really angry older white voter who dislikes Obama … but has absolutely no ideological underpinnings, then I guess that term would apply to Trump and his followers," said a Republican strategist who has advised both insurgent and establishment-aligned GOP candidates.