HOUSTON (AP) — The National Rifle Association kicked off its annual convention Friday with a warning to its members they are engaged in a "culture war" that stretches beyond gun rights, further ramping up emotions surrounding the gun control debate.

NRA First Vice President James Porter, a Birmingham, Ala., attorney who will assume the organization's presidency Monday, issued a full-throated challenge to President Barack Obama in the wake of a major victory regarding gun control and called on members to dig in for a long fight that will stretch into the 2014 elections.

More than 70,000 NRA members are expected to attend the three-day convention amid the backdrop of the national debate over gun control and the defeat of a U.S. Senate bill that would have expanded background checks for gun sales. It was introduced after December's mass shooting at a Newtown, Conn., elementary school. A small gathering of gun control supporters were outside of the convention in Houston.

Porter's remarks came in a short speech to about 300 people at a grass-roots organizing meeting and set the tone for a "Stand and Fight"-themed convention that is part gun trade show, political rally and strategy meeting.

"This is not a battle about gun rights," Porter said, calling it "a culture war."

"(You) here in this room are the fighters for freedom. We are the protectors," said Porter, whose father was NRA president from 1959-1960.

Rob Heagy, a former parole officer from San Francisco, agreed with Porter's description of a culture war.

"It is a cultural fight on those 10 guarantees," he said, referring to the Bill of Rights in the U.S. Constitution. "Mr. Obama said he wasn't going after our guns. As soon as the Connecticut thing happened, he came after our guns."

That theme carried throughout the day and reached a crescendo in a 3 ½-hour political rally punctuated by fiery speeches from state and national conservative leaders.

"You stood up when freedom was under assault and you stood in the gap, you made a difference," former U.S. senator and Republican presidential candidate Rick Santorum told the cheering crowd of more than 3,500 at the rally.

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"This is a critical time in American history. Something big is happening in America," Santorum said. "Stand for America. Fight for America."

Texas Gov. Rick Perry criticized gun control supporters as opportunists who prey on the raw emotions of tragic events.

"You can almost set your watch for how long it takes for people who hate guns, who hate gun owners, to start a new campaign," after a mass shooting, Perry said.

Obama, who has pushed for gun control measures, was a prime target for criticism the entire day. NRA Executive Director Chris Cox bragged about the organization's political victory.

"It was great to see the president throw a temper tantrum in the Rose Garden," Cox said.

Josh Horwitz, executive director of the Coalition to Stop Gun Violence, called the culture war reference a sign the NRA is worried about polls that show most Americans support some expansion of background checks.

"They want to make it a culture war," Horwitz said. "They have to make it into something bigger. On the issue of background checks, they can't possibly win."

Gun control advocates were determined to have a presence outside the convention hall. Across the street Friday, the No More Names vigil read the names of gun violence victims since the Sandy Hook Elementary School massacre. Gun control advocates also planned a petition drive to support expanded background checks and a Saturday demonstration outside the convention hall.

Erica Lafferty, whose mother, Sandy Hook principal Dawn Hochsprung, was killed by the gunman, was outside the building and said she hoped to talk to as many NRA members as she could.

"I am not against people owning guns. I am asking for safe and responsible gun ownership and gun laws. I don't understand where the problem is with background checks," Lafferty said.

While national polls have shown that a majority of Americans are in favor of expanding background checks, many convention attendees said Friday they were not in favor of such efforts.

"We already have something like those laws now. We don't need new laws on top of the old laws. They need to enforce the laws that we have," said Charles Henderson, 59, a farmer from Amarillo, Texas.

Inside the hall, visitors strolled past acres of displays of rifles, pistols, swords and hunting gear. Under Texas law, attendees could carry concealed weapons with a permit.

Debbie and Daniel Ferris of Gun Barrel City, Texas, attended the grass-roots organizing workshop and agreed with Porter's assessment of a culture war.

"It's about fighting tyranny," said Debbie Ferris, who has been an NRA member for five years. Her 35-year-old husband is a lifetime member.

"We don't like to be pushed around," Daniel Ferris said. "We are free Americans."

Sarah Palin, the former Republican vice presidential nominee and ex-Alaska governor, spoke to personal freedoms at the political rally as well, saying NRA members should "keep the faith" and "stand up and fight for our freedoms."

But gun control supporters promise to keep pressing the issue and have made significant strides at the state level.

Sen. Joe Manchin, a West Virginia Democrat, has said he will re-introduce the bill to require criminal and mental health background checks for gun buyers at shows and online.

Colorado lawmakers recently passed new restrictions on firearms, including required background checks for private and online gun sales and a ban on ammunition magazines that hold more than 15 rounds. Connecticut added more than 100 firearms to the state's assault weapons ban and now requires background checks for private gun sales.

Maryland and New York have passed sweeping new guns laws, and in Washington state, supporters of universal background checks recently announced a statewide campaign to collect 300,000 signatures to take the issue straight to voters.

"There are 90 percent of Americans that support this," Lafferty said. "We are not going away. It's a huge issue."