Former U.S. Senator Fred Thompson's expected entry into the 2008 presidential campaign is likely to shake up the battle for the Republican Party nomination. VOA National correspondent Jim Malone has more from Washington.

Fred Thompson waits to speak at  Lincoln Club in Newport Beach, California, 4 May 2007

Thompson served as a U.S. senator from Tennessee during the 1990s and first came to public attention as a Republican lawyer on the Senate Watergate committee during the presidency of Richard Nixon in the mid-1970s.

But perhaps Thompson's biggest political asset is that he is well known as an actor in movies and on the popular long-running television series Law and Order.

Thompson supports President Bush on Iraq and favors a strong approach on national security and on curbing illegal immigration.

He recently spoke to a Republican group in California.

"We live in a world where 40 countries have fissile material sufficient to make a nuclear weapon and the bad guys are trying their best to get their hands on it," he said. "And we live in a country with porous borders and porous ports. It does not take a genius to put all that together and see the problem that we have got in this country."

Thompson is running third or fourth among Republican contenders in most public opinion polls, a reasonably strong position given that he is not yet an official candidate.

But getting into the race late would mean Thompson would have to scramble to raise money to compete with the current Republican frontrunners who have been out campaigning and raising money for months.

Republican presidential hopefuls Mitt Romney, left, embraces Rudy Giuliani, as John McCain walks by after Republican debate, 15 May 2007

Several surveys suggest about a third of Republican voters have not settled on a presidential candidate and would welcome either Thompson or former House of Representatives Speaker Newt Gingrich joining the race.

"There is a level of dissatisfaction and unhappiness with the top tier of the Republican presidential candidates," said Tom DeFrank of the New York Daily News, who was a guest on VOA's Issues in the News program. "Many Republican conservatives have problems for different reasons with all of them and they are looking for somebody else. They are looking for somebody who is more like Ronald Reagan."

Thompson is conservative on social issues like abortion and that appeals to religious conservatives, a key constituency in the Republican Party.

In addition, the lengthy campaign could cause some voters to tire of the current crop of candidates and look for a new face.

"You know, the people who are very prominent now and appear to be the potential winners may fade and people may lose interest in them," said Ross Baker, a political expert at Rutgers University in New Jersey. "Their campaigns may falter."

The Republican field is already crowded with 10 contenders.

In the Democratic race, eight candidates are vying for the party nomination. Some Democratic activists continue to urge former Vice President Al Gore to join the race, but so far he has declined.

The top Democratic contenders at the moment are New York Senator Hillary Clinton, Illinois Senator Barack Obama and former North Carolina Senator John Edwards.