Kenneth R. Timmerman, a freelance investigative reporter from Kensington, yesterday added his name to the list of Republicans who want to challenge Democratic U.S. Sen. Paul S. Sarbanes next year.

Timmerman, 46, joins Paul H. Rappaport, a Howard County lawyer, and Robin Ficker, a former House of Delegates member from Montgomery County, in the race for the Republican nomination. The international affairs expert and one-time teacher kicked off his grass-roots campaign from the front porch of his Kensington home yesterday, his wife, Christine, and three of their five children standing beside him.

"I am running to restore people's faith in government," Timmerman said to a group of about a dozen supporters and neighbors. He hopes to do that by supporting school vouchers, overhauling the tax system, privatizing Social Security and instituting a national missile defense.

Timmerman, who has never held public office, says he knows he has a hard fight ahead to win the March 7 primary and ultimately replace Sarbanes, who is seeking a fifth term. Rappaport, a former Howard police chief who ran unsuccessfully for lieutenant governor in 1994 and attorney general in 1998, entered the Senate race last month with a campaign platform advocating a stronger military and crime victims' rights. Ficker, known for anti-tax referendum drives that he has led in recent years in Montgomery, is focusing on making the state drug free, cutting taxes and wasteful spending and improving transportation.

Timmerman said his 17 years as an investigative reporter, many of them spent overseas, will give him an edge on foreign affairs issues.

"My strengths are going to be attracting grass-roots support and in international issues," said Timmerman, who is a contributing editor to Reader's Digest and a frequent writer for the American Spectator.

He said he will file formally to run this week. After the gathering at his house, he traveled to Columbia yesterday to make a second front-porch announcement at the home of a supporter.

Timmerman, originally from Bucks County, Pa., said he started his journalism career at USA Today in the early 1980s and eventually wound up working in Paris. He has been freelancing for several years and has written extensively about the Iran-Iraq conflict and the Clinton administration's relationship with China.

Timmerman started an exploratory committee several months ago, and he has been talking to Republican clubs across the state ever since.

"People are eager for a change, they're eager for competence in the U.S. Senate," he said.

CAPTION: With Kenneth R. Timmerman as he announces are, from left, family friend Chris Lemos; daughter Diana, 10; son Simon, 6; daughter Clio, 19; and wife Christine.