WASHINGTON — In an election season in which the Republican Party’s leaders and pollsters are advising GOP candidates to emphasize the economy and avoid the Iraq war and national security, Pennsylvania’s junior senator prefers to address hometown crowds by invoking the nearly unpronounceable name of the Iranian president.

When Senator Santorum is on the stump, he delivers “The Gathering Storm,” a speech named after the first volume of Winston Churchill’s history of World War II. In the speech, he lists recent threats and atrocities perpetrated by Islamist terrorists and orchestrated by Iran. He follows each threat and atrocity with the refrain, “This is evil.”

He also warns that Iran’s ruling mullahs are forging alliances with socialist leaders in Venezuela and North Korea. “I am here again today talking about this issue because Islamic fascism continues to rear its ugly head,” he says. “And because it is being joined by others, becoming a hydra.”

On Sunday, Mr. Santorum accused his opponent, state Treasurer Robert Casey Jr., of refusing to divest the state’s pension funds from American companies that do business with Iran. In response, Mr. Casey’s campaign said the Bush administration had refused to hand over a list of those companies when asked.

While vulnerable Republican incumbents in Virginia, Ohio, and Montana are running advertisements attacking Democrats for raising taxes, Mr. Santorum is criticizing Mr. Casey for being too passive on national security. One recent Santorum ad features footage of a North Korean missile launch spliced with pictures of President Ahmadinejad of Iran, a nuclear mushroom cloud, and Chinese oil platforms near American shores. An announcer ends the 30-second montage by saying, “We just can’t take a chance on Bob Casey.”

In a difficult election season for Republicans, Mr. Santorum’s unusual campaign may serve as a referendum on the political viability of the Bush doctrine and neoconservatism, particularly if Democrats win control of the House.

The tenor and tone of the Santorum campaign also defies the wisdom of his party. Last month, Majority Leader Frist, a Republican of Tennessee, told GOP candidates to focus on pocketbook issues and avoid discussing the war in Iraq and national security — a first for Republicans, who embraced the two issues in 2002 and 2004. When asked Sunday for his opinion of Defense Secretary Rumsfeld, the GOP Senate candidate in Maryland, Michael Steele, told NBC’s “Meet the Press,” “He wouldn’t be my choice.”

In an interview yesterday, Mr. Santorum shrugged off his party’s advice. “I think I have a better understanding of what is going on in the minds of people in Pennsylvania than pollsters based in Washington,” the two-term senator said. “I run my campaign based on the important issues of the day.”

“This stuff needs to be said and I need to say it,” he added.

So far, his approach has not translated to better poll numbers. A survey yesterday of likely voters from Pennsylvania’s West Chester University had Mr. Casey at 50% and Mr. Santorum at 39%. Recent polls show that Mr. Santorum is trailing his challenger by an average of 12 percentage points.

But Mr. Santorum is not worried. He said his campaign’s internal polls have him trailing the state treasurer by “six or seven points.”

“We have a little over a week to go. Back in 1994, we were six or seven points to go,” he said. “We are going to see a growing intensity among our voters. The one thing we see here is not a whole lot of intensity for him. It is sort of an anti-Bush vote and anti-Santorum vote he’s banking on. We think we have the machine in place to beat him.”

Other observers, however, see the senator’s decision in the last weeks of his campaign to focus on foreign threats as a Hail Mary pass that is not likely to work. “This is the most remarkable change of strategy at the end of a campaign I have ever seen. It is almost like he has thrown caution to the wind,” G. Terry Madonna, a political science professor and pollster at Franklin and Marshall College in Lancaster, Pa., told The New York Sun. “He has forsaken any effort to make this about his seniority, his experience, the millions he has brought home in appropriations. He has turned this into a debate on the future of the country.”

Mr. Santorum, however, said he has emphasized national security all along. He pointed to his sponsorship of the Iran Freedom and Support Act, which was signed into law with modifications in September. The senator tried to force a vote on the bill in June, over the objections of Secretary of State Rice.

“No offense to the president, but I think I am making a better case than the president on the war. I wish he would make the case a little stronger,” Mr. Santorum said.

But the president of Americans for Tax Reform, Grover Norquist, expressed skepticism about Mr. Santorum’s strategy. “The guy in Pennsylvania is running on Iran and Iraq, which others thought is not the most vote-winning strategy,” he told the Sun. “If he loses, then people will say, ‘He was wrong.’ If it turns out he wins, that could change politics. It will be very interesting to see.”

Mr. Norquist, who himself helped change American politics in the 1980s by asking state and federal candidates to sign pledges not to raise taxes, represents conservatives who could blame the Iraq war and the Bush doctrine if Republicans lose control of the House next month.

“The polls suggest he is not winning at present,” Mr. Norquist said. “If by using this strategy he turns this election around, then neoconservativism has a place at the table of politics in the future.”

Not surprisingly, other neoconservatives do not see the Santorum race in those terms. A foreign policy adviser to President Bush during his 2000 campaign, Richard Perle, said yesterday that Mr. Santorum’s pedigree as a social conservative is hurting him in Pennsylvania. “There are people who will want to assess the race as an outlook on foreign policy and national security, on the issues Santorum has emphasized, such as Iran,” Mr. Perle said. “But in fact I think Santorum’s problem lies with his approach to such domestic issues as stem cell research, the Terry Schiavo case, and other sociopolitical questions. He is just a little too extreme on these issues for the Pennsylvania electorate.”

A former speechwriter for Mr. Bush, David Frum, told the Sun: “It would be as silly to look at the Santorum race and say the Republican Party has no place for hawks as it would be to look at the race and say the Republican Party has no place for pro-lifers.”

For now, Mr. Santorum has no intention of changing course, he said. “There are countries like Iran who would like to see the United States and Israel no longer exist. I know it is unpopular to talk about this stuff. But this is the issue the American public needs to be aware of.”