WASHINGTON -- As tensions over Iran's nuclear ambitions escalate, Sen. Rick Santorum has become louder and more aggressive in advocating for regime change, for harsher penalties on foreign companies that invest in Iran's energy industry and for isolating the Islamic republic's leaders.

Mr. Santorum says direct talks with Iranian leaders, which some of his colleagues as well as his Democratic opponent, Auditor General Bob Casey, support, would be pointless.

"These are people who see negotiation as weakness -- I think we have to show strength and resolve to remove this government through peaceful means and through support of the Iranian people both in Iran and outside," said Mr. Santorum.

That tough talk by the Pennsylvania Republican and his harsh denunciations of Iran's president -- whom he refers to as "a maniac" -- has won him admirers and campaign contributors, particularly among supporters of Israel.

He ranks among the top five Republicans in Congress in receiving money from pro-Israel groups this cycle with $52,000 coming from pro-Israel political action committees alone, according to the Washington-based Center For Responsive Politics.

Some of his critics view his position, amid a tight re-election campaign, as a transparent attempt to pump up his national security credentials and draw attention away from growing discontent over U.S. policy in Iraq.

Although Mr. Santorum has pushed legislation this year to get tougher on Iran, a number of scholars studying Iran-U.S. relations said they were skeptical whether the legislation would have any practical effect.

His legislation -- and the companion legislation already passed by the House -- would require mandatory U.S. sanctions on any person or company that helps Iran obtain technology to develop weapons of mass destruction or acquire "destabilizing numbers" of advanced conventional weapons.

Mr. Santorum has also advocated increasing aid to groups within Iran that favor non-proliferation and to groups that support overthrowing the current regime to establish a democracy.

Outside Congress, Mr. Santorum has urged the United Nations to consider forbidding travel by Iran's leaders, pursuing legal action against Iranian leaders for alleged human rights and terrorism violations, grounding international flights on Iran Air and barring the transport of cargo on ships owned by Iran's government.

Hopes for success doubted

Two of the Iran policies Mr. Santorum has embraced -- increasing aid to democracy promotion programs and enforcing more stringent penalties on foreign companies investing in Iran -- are popular among many of his Democratic and Republican colleagues in Congress.

But a number of scholars on U.S.-Iranian relations said they would not expect either initiative, if approved, to have a substantive effect.

Earlier this year, the Bush administration requested $75 million for pro-democracy efforts in Iran, including the funds in an emergency spending measure primarily focused on military operations in Iraq and Afghanistan.

If the package is approved by a House-Senate panel, a portion of the $75 million would go toward expanding pro-democracy satellite, radio and television broadcasting into Iran. But Hadi Semati, an associate political science professor at the University of Tehran and public policy scholar at the Woodrow Wilson International Center for Scholars in Washington D.C., said additional satellite broadcasts would likely exacerbate the already tense situation by reinforcing the view that the U.S. is "after regime change."

Mr. Semati also said he could not imagine that any groups involved in Iran's struggling democratic movement would seek financial aid from the U.S. because doing so would expose them to closer scrutiny from the Iranian government at a time when leaders are stepping up arrests for activities viewed as undermining the current regime.

Mr. Semati said increases in aid for those programs "puts the reformists -- and those who are in favor of dialogue and change and reform -- in more danger.

"It becomes a pretext for more repression, more closure," he said. "Activists across the board argue that this is not going to help anybody. Just don't do it -- that is basically, I would say, the consensus in Iran among the [non-governmental organization] community and activists."

Abbas Milani, the co-director of the Iran Democracy Project at the Hoover Institution at Stanford University, said congressional resolutions advocating regime change are also unhelpful because the U.S. government cannot be viewed as trying to engineer a movement that must come from within Iran.

"The U.S. can, at best, be an aid to this process," Mr. Milani said. "It cannot be the initiator of the democratic movement. ... It can be an outside, limited, but important source of help. If that humility is there, then I think there is certainly a role to be played."

Mr. Milani did say that sanctions such as the travel ban on Iranian leaders could be effective as a symbolic gesture that -- unlike economic sanctions -- could send the message to the Iranian people that "the fight is not with them, but the regime."

There is widespread skepticism in the academic community over Mr. Santorum's proposal to extend and modify the soon-to-expire Iran-Libya Sanctions Act, which Congress passed in the mid-1990s after President Clinton barred U.S. trade with and investment in Iran.

The Iran Libya Sanctions Act, which no longer applies to Libya, placed penalties on foreign companies that invested more than $20 million in Iran's energy sector in a given year.

Theoretically, companies investing in Iran's energy sector faced the denial of certain U.S. bank loans and restrictions on imports, but European Union members and other trading partners fiercely opposed the sanctions.

And under both the Bush and Clinton administrations, the United States has not penalized a single company under the act even though foreign firms have invested more than $11.5 billion in Iran's energy sector since 1999, according to a Congressional Research Service report.

That is exactly why pro-Israel groups such as AIPAC have been pressing Congress to make some of the changes Mr. Santorum has suggested.

While some Iran experts argue that the sanctions act has been completely ineffective and could continue to be ineffective even with the proposed changes, Clifford Kupchan of the Eurasia Group said the law has had some effect by impeding some development in the Iranian gas sector and by making international oil companies "look over their shoulder," he said, before investing in Iran.

Under the changes proposed by Mr. Santorum -- and under a more restrictive House version that would cut foreign aid to the countries whose companies violate the act -- the White House would have to provide more justification for waiving sanctions on Iran energy deals, and must make a decision within 90 days about whether an investment by a foreign company violated the act must make a decision with 90 days on whether an investment by a foreign company violated ILSA, instead of allowing cases to languish indefinitely.

But administration officials are opposing some of the modifications -- particularly because they are relying more than ever on cooperation from their allies -- as they craft a solution to diffuse tensions with Iran.

"I think right now the administration is between a rock and a hard place," Mr. Kupchan said. "They need European companies to join them in U.N. efforts and coalition of the willing efforts to put sanctions on Iran. ... On the other hand, it's a major priority of the administration to stop investment, especially in the energy sector."

Mr. Santorum says his staff is working through some of the administration's concerns with the legislation in the hopes of finding an agreement before the act expires in August.