Hearings on the radicalization of Muslim Americans set to begin today in the House have provoked a volatile national debate that is spilling into the election cycle.

Threatening phone calls made this week to Rep. Peter King, chairman of the Homeland Security Committee, were the latest sign that tensions are high as the New York Republican spearheads a probe into the threat of domestic terrorism.

Battle lines are already being drawn. On one side are Muslim advocacy and civil rights groups that call the investigation a targeted witch hunt and liken it to Joe McCarthy’s anti-communism hearings. On the other are national security and tea party activists who argue that the inquiry is a necessary first step toward protecting Americans.

King told Roll Call that he initiated the probe to highlight what he says is a rising threat of radicalization in Muslim communities. The hearings could stretch out over the next year, prolonging the topic just long enough to make Islam a wedge issue in the presidential primaries.

“We’re starting to see increased anti-Muslim rhetoric and bigotry that seems timed for the political season,” said Farhana Khera, executive director of Muslim Advocates. “The Republican Party is increasingly painting itself as the party of hate and divisiveness.”

As candidates travel around the country testing the waters for presidential runs, the hearings could also revive last year’s polarized debate on a proposed Islamic center, which critics dubbed a mosque, near the site of ground zero in New York City. In the midterm elections, some conservative candidates used that issue to generate cash and attention for their campaigns.

Khera’s nonprofit and 50 other Muslim and interfaith groups sent a letter to Congress last month protesting the hearings and raising concerns about what they see as anti-Muslim comments by King that there are too many mosques in the U.S. and that “80 percent of the mosques were controlled by extremists.” The groups say the contrary is true and point to a Triangle Center on Terrorism and Homeland Security study showing Muslims have worked with law enforcement — 48 of 120 known terrorist plots since 9/11 were foiled with tips from the Muslim community.

King said that his goal is not to target Muslims but to engage them on matters of national security and that he resents suggestions that his motivations are political.

“To me there’s nothing political about Sept. 11. There’s nothing political about fighting Islamic terrorism. … That’s the only charge made against me I resent,” he said. “I’m not concerned about the politics of it. I don’t see how it in any way could divide Republicans.”

But Republican strategist Suhail Khan does. The former Bush administration political appointee started the Conservative Inclusion Coalition to advise the Republican National Committee on the sensitivities of cultural and religious minorities.

Khan said he worries candidates testing the waters for presidential runs will use the debate as “a partisan or political device to generate animosity of Muslims Americans and, worse, to raise money for particular candidates who are trying to place themselves on either side of the issue.”

During the midterms, Khan joined leaders of conservative groups in criticizing members of his own party who tried to use the mosque debate to attack opponents. He pointed to some who did and lost, including New York gubernatorial candidate Rick Lazio and Tennessee Congressional hopeful Lou Ann Zelenik, as proof that the strategy does not work.

“The risk is that when the electorate is focused on real bread-and-butter issues, such as jobs, economy and taxes, that by bringing up these kinds of issues, not only are they wasting time, they might even lose votes,” Khan said. “These issues are like shiny objects to raccoons. They’re just distractions.”

At least one portion of the electorate may be keen to take on the issue. Conservative activists with the hard-liner group ACT! for America and some tea partyers rallied behind King and organized events to counter the opposition. While leading tea party groups have not yet taken a position, Tea Party Patriots Orange County Coordinator Marc Harris said activists in California are watching closely.

“We’re all talking about it. It hasn’t become an official tea party issue, but all the members of the tea parties are concerned about it and have an opinion about it,” he said. “It probably will become something that we will add to our national dialogue.”

A recent protest organized by conservatives in his county highlighted the rising tensions. As supporters of the Islamic Circle of North America entered a fundraiser there, protesters gathered outside with American flags and shouted, “You’re not welcome here. Go home,” and “Take the sharia and go home, you terrorist lovers.”

Video footage has since circulated online and prompted counterprotests. Muslim Advocates’ Khera said she is concerned the hearings could stoke such hostilities. Her group launched a website, WhatUnites.Us, to log anti-Muslim rhetoric as the hearings get under way.

But Karen Lugo, who helped organize the California protest and condemned the heckling, said Congressional action could help soothe her community’s concerns.

“I am confident that when people understand that the government is beginning to address this question, the sense of security and trust that government is looking to this, I think that will calm this situation,” she said.

Witnesses for the first hearing suggest the hearings may not be as one-sided as opponents portray. King has invited Rep. Keith Ellison (D-Minn.), a Muslim and vocal critic of King’s plans, to testify.

“Most Muslims, especially after they see the hearings, will see how fair they are,” King said. Also testifying today are the relatives of two accused terrorists, along with Los Angeles County Sheriff Leroy Baca, Muslim conservative Zuhdi Jasser and Rep. Frank Wolf (R-Va.).

Among Congressional leaders, sentiments on the hearings seem to run along party lines. Senate Majority Leader Harry Reid (D-Nev.) said Tuesday that he is “deeply concerned” about the hearings, as did House Minority Leader Nancy Pelosi (D-Calif.) and Minority Whip Steny Hoyer (D-Md.). House Majority Leader Eric Cantor (R-Va.) defended them.

“We have got demonstrable occurrences in this country that show we’ve got a risk of the spread of radical Islam. That’s not within the security interests of the United States and its citizens. It’s something that we really want to work with folks to see if we can stop,” Cantor said.

While President Barack Obama has avoided direct comment, Deputy National Security Advisor Denis McDonough offered indirect criticism while visiting a Virginia mosque recently: “We must resolve that, in our determination to protect our nation, we will not stigmatize or demonize entire communities because of the actions of a few. In the United States of America, we don’t practice guilt by association.”