Alarmed by a resurgence of more establishment Republicans, activists are pressuring them to “recommit’ on their opposition to abortion, gay marriage and illegal immigration. (Rick Bowmer/AP)

Although many Republicans are optimistic about their chances in this year’s elections, some of Washington’s leading conservatives gathered Thursday to privately vent frustrations about what kind of party they will be left with after November.

The group, alarmed by a resurgence of the GOP establishment in recent primaries and what activists view as a softened message, drafted demands to be shared with senior lawmakers calling on the party to “recommit” to bedrock principles.

Some of those principles laid out in the new document — strict opposition to illegal immigration, same-sex marriage and abortion — represent the hot-button positions that many Republican congressional candidates are trying to avoid as the party attempts to broaden its appeal.

Several attendees said they fear that elected Republicans, even if they succeed in retaining control of the House and winning the Senate majority, would cast aside the core conservative base.

“Conservatives ought not to delude themselves that if Republicans win the Senate majority, it will somehow be a conservative majority,” said L. Brent Bozell III, president of the Media Research Center, which monitors perceived media bias. “We should have no expectation whatsoever that they will listen. That’s why we’re fighting.”

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Others worry that a toned-down campaign message by the party would dim GOP turnout and undercut Republicans in competitive races.

“I’m terrified that Republicans will blow this election if they are not going to stand for something,” said Michael A. Needham, the chief executive of Heritage Action, a conservative group.

Thursday’s gathering at the Ritz-Carlton in Tysons Corner, Va., was coordinated by Reagan-era attorney general Edwin Meese III and former congressman David McIntosh (Ind.) as part of an initiative called the Conservative Action Project.

It included dozens of leaders from across the conservative movement, including tea party organizer Jenny Beth Martin and interest group executives such as Grover Norquist of Americans for Tax Reform and Tony Perkins of the Family Research Council. The meeting, which featured speeches from Sens. Ted Cruz (Tex.) and Mike Lee (Utah), marked the first time this year that prominent national conservatives have come together to candidly assess the GOP and their strategy for shaping it.

The day-long session underscored how simmering tensions between rival factions in the Republican Party appear to be growing, even as polls point to the potential for a major GOP victory in midterm elections in the fall.

Congressional Republicans have been grappling over whether to compromise on immigration, some Republicans are calling for a smaller military, and same-sex marriage is fading as a top issue in this year’s campaigns.

Meanwhile, mainstream GOP business groups such as the U.S. Chamber of Commerce have lifted establishment candidates to victory in a Senate primary in North Carolina and a special House election in Florida. Senate Minority Leader Mitch McConnell (Ky.) is expected to easily defeat a tea party challenger in his primary Tuesday.

Many GOP strategists and party leaders think that tea party activists’ successes in recent years nominating ideological purists resulted in weak candidates and crippling general-election losses. They worry that efforts to revive the base could threaten Republican hopes again.

“What’s clear is that we ought to be focusing on economic security for the future, not divisive social issues. That’s how we lost several key Senate races last cycle and plays into the Democrats’ hand,” said GOP consultant Brian Walsh, a former communications director for the National Republican Senatorial Committee.

As conservative leaders mingled Thursday over coffee and deli sandwiches, they sounded exasperated about the way the party appears to be siding more with its cautious leadership, rather than making an aggressive conservative pitch.

In the 10-page pamphlet finalized Thursday, they called on party leaders to champion lower taxes, a well-funded military, and the idea that “married moms and dads are best at raising kids.” The document warns Republicans against signing on to an immigration overhaul unless the U.S. border is “fully secure,” and it argues that support for school prayer, a balanced-budget amendment and antiabortion legislation should remain priorities.

But even in the tightknit room, there was not universal agreement. Norquist, for example, supports legalization for many illegal immigrants and has pushed for more scrutiny of the defense budget. In an interview, he said he attended Thursday’s meeting to back the broad efforts on the right to unite, rather than endorse the document line by line.

Most activists expressed dismay that they seemed to have a diminished voice in the party.

“What we’re doing and saying is not resonating, so we are trying to come to grips with that,” said Grace-Marie Turner, the president of the Galen Institute, a conservative research group. “We have to learn to relate our solutions to people’s struggles.”

Some said conservatives had not made their case effectively, and different leaders offered their own visions for the right approach.

Wesley Denton, a senior adviser to Heritage Foundation President Jim DeMint, led a panel called “Breaking Through With a Conservative Message,” and Citizens United President David Bossie spoke about the power of expressing conservatism through films, of which he has produced several.

Perkins led a panel on restoring the “traditional family” as a priority for the party. Thomas J. Fitton, president of Judicial Watch, which has obtained documents related to the 2012 attack on an American diplomatic mission in Benghazi, Libya, talked up his group’s ability to pressure the White House through Freedom of Information Act requests.

Alfred S. Regnery, a conservative lawyer and former publisher, said the group convened “to provide the substance to Republicans and guide them. That’s the way this is supposed to work — they should be listening to us.”

Cruz, who has clashed with top Senate Republicans over budget issues and is considering a presidential bid in 2016, told the crowd members that they are still the party’s most influential bloc.

“Some say, ‘Yay, our team is winning,’ ” he said, referring to Republicans’ confidence about possibly taking control of the Senate. “But we win when we stand for principle and we lose when we give in to Washington’s status quo.”

Many there likened the session to one that took place in 1960, when the late National Review editor William F. Buckley Jr., Bozell’s uncle, met with allies to craft a statement of principles for a young conservative movement.

Bozell, Meese and many of the same people at the Ritz-Carlton on Thursday had held a similar session in 2010, ahead of the tea-party-led GOP sweep that year.

To guide them on Thursday, the 2010 principles, called the Mount Vernon statement because it had been signed on the Alexandria estate once owned by George Washington, was displayed throughout the day next to the ballroom podium.