So far the Republican campaign for president has been fairly restrained, with the ever-growing field aiming most of their attacks at Hillary Clinton and President Obama. But the upcoming vote in Congress on reauthorizing the Patriot Act could open the first real fissures in the GOP field.

Unless Congress takes action, most provisions of the Patriot Act will expire on June 1. In response, Senate Majority Leader Mitch McConnell is pushing a bill to make the controversial surveillance law permanent, and without any significant revisions. That bill is backed by Senate Intelligence Committee Chairman Richard Burr (R., N.C.) and most Senate Republicans.

However, the House is taking a very different approach. Last week, the Judiciary Committee voted 25 to 2 in favor of a bipartisan bill that would reauthorize the Patriot Act for five years, while imposing greater privacy protections such as reining in the National Security Agency’s bulk-collection and metadata programs. Speaker John Boehner is backing this version of the reauthorization, which is expected to pass the full House within the next couple of weeks.

The upcoming vote in Congress on reauthorizing the Patriot Act could open the first real fissures in the GOP field.

The split is forcing Republican presidential candidates to take sides. Among the most prominent backers of the House approach is Senator Ted Cruz. Reauthorizing the law without changes “is not acceptable,” Cruz said in a statement. “It is absolutely critical for Congress to balance the privacy interests of law-abiding citizens against the public’s interest in national security.” But neither the current House reauthorization bill nor the USA Freedom Act, introduced in 2013 but never passed during the 113th Congress, goes far enough for Senator Rand Paul, who will oppose reauthorization all together. Paul says that “Our founding fathers would be mortified” by the government’s spying on U.S. citizens without a warrant.

On the other hand, Senator Marco Rubio strongly supports reauthorization and opposes the House reforms. “By and large, I’m supportive of the NSA programs and for extending [them],” Rubio told reporters. “I think they are important for the security of our country.” He will likely back the McConnell version, arguing that “the changes being proposed seem to be a reaction to misinformation and alarmism not rooted in the reality.”

Senator Lindsey Graham has long been a vocal supporter of both the Patriot Act and the NSA surveillance program. He is also expected to back the McConnell bill, and to oppose any restrictions on the metadata program.

Those candidates who are not in the Senate won’t have to vote on the issue, but they are being forced to weigh in anyway. Jeb Bush, for instance, has strongly backed the Patriot Act, going so far as to say that President Obama’s willingness to continue Bush-era surveillance programs is “the best part of the Obama administration.” In a foreign-policy speech in Chicago, Bush said the mass surveillance is an essential ingredient in the War on Terror. Fighting terrorism, he declared, “requires responsible intelligence gathering and analysis, including the NSA metadata program, which contributes to awareness of potential terrorist cells and interdiction efforts on a global scale.… This is a hugely important program to use these technologies to keep us safe.”

Bush was joined by Chris Christie, both in backing Patriot Act reauthorization and in praising the Obama administration’s surveillance programs. “President Obama has done nothing to change the policies of the Bush administration in the war on terrorism. And I mean practically nothing,” Christie said. “And you know why? Because they work.”

Others have been somewhat more circumspect. Bobby Jindal has not directly addressed Patriot Act reauthorization, but he has generally supported mass surveillance, including the metadata program. Rick Santorum has also been generally supportive of the program. But Rick Perry has been more critical, agreeing that some surveillance is crucial to national security but admitting that he was shocked by the revelations about NSA spying. “You would expect to hear those stories coming out of China,” Perry told reporters when Edward Snowden’s revelations first broke. Mike Huckabee, who announced his candidacy yesterday, has not formally commented, but in Facebook posts has been even more critical of the NSA, writing that the agency “routinely violated the rules and invaded Americans’ privacy.” In another post, he wrote, “I would think it’s unconstitutional even to have a secret court that rules on citizens’ civil rights without them knowing it.” Scott Walker, as has been his habit lately, is straddling the issue, avoiding any specific position on reauthorization, while generally suggesting that we need to balance civil liberties with security.

Already the candidates have begun to throw barbs at one another.

Cruz has criticized Paul for his vote last fall against the USA Freedom Act, which Cruz cosponsored with Senator Mike Lee (R., Utah). That bill would have reauthorized the Patriot Act with restrictions on NSA surveillance similar to those now in the House bill. The bill fell two votes short of the 60 necessary to block a filibuster, and Cruz says that Paul’s no vote sank “our single best chance to end the bulk collection of metadata.”

A Paul spokesman countered that “Others are welcome to their decision to compromise on Americans’ Fourth Amendment rights, but not to cast it misleadingly as a vote for liberty.” Paul also criticized Bush, tweeting, “Sadly, one GOP candidate thinks the NSA’s violation of your rights is ‘very important.’ ”

As the campaign moves on, we should expect the candidates to increasingly set out their differences. The debate over Patriot Act reauthorization and NSA spying provides an important, and healthy, opening salvo.