PROVIDENCE — The Democratic front-runners for the 2008 presidential nomination, Senators Hillary Clinton and Barack Obama, would each beat any of three top Republican candidates among Rhode Island voters, according to a new survey by Brown University.

The same poll found that just 16 percent of Rhode Islanders believe Republican President Bush is doing an excellent or good job.

The poll is based on a statewide random sample of 475 registered voters in Rhode Island. Overall, the poll had a margin of error of about plus or minus 5 percentage points.

Thirty-six percent of local Democrats say they haven’t decided which candidate to support in the primary. Clinton, D-N.Y., is favored by 33 percent of likely Democratic primary voters; Obama, D-Ill., is the choice of 15 percent; 8 percent favor former Sen. John Edwards of North Carolina.

Four percent would vote for Sen. Joseph Biden, 2 percent favor Sen. Christopher Dodd of Connecticut, 1 percent support Bill Richardson, 1 percent favor Tom Vilsack, and 0 percent want Dennis Kucinich.

The margin of error for the poll’s Democratic primary sample is about plus or minus 6 percentage points.

If the presidential general election was held today and the nominees were Democrat Clinton and Republican Sen. John McCain of Arizona, 49 percent said they would support Clinton, 36 percent favor McCain, and 15 percent are undecided. Obama would top McCain 40 to 37.

If the GOP nominee is former New York Mayor Rudy Giuliani, who was in Providence on Saturday night for a fundraiser, Clinton has a lead of 49 to 37 percent, with 14 percent undecided. Obama would lead Giuliani 43 to 38.

And if the Republican choice is former Massachusetts Gov. Mitt Romney, Clinton is favored by 56 to 26 percent, with 18 percent undecided. Obama would lead Romney 52 to 26.

When questioned about the job performance of state officials, 59 percent said Governor Cariceri is doing a good job; 40 percent think Attorney General Patrick C. Lynch is doing a good job, down from 51 percent in September; 67 percent favor the job performance of Providence Mayor David Cicilline; 26 percent believe House Speaker William Murphy is doing a good job; and 19 percent said the same about state Senate President Joseph Montalbano.

Three recently installed general officers — Lt. Gov. Elizabeth Roberts, Secretary of State A. Ralph Mollis and state Treasurer Frank Caprio Jr. —have apparently not yet made a deep impression on Rhode Island voters, with nearly 60 percent reporting they are “unsure” about the job performances of the three new general officers, who were elected in November.

The survey was conducted Saturday at Brown by Darrell M. West, director of the Taubman Center for Public Policy and the John Hazen White Sr. Public Opinion Laboratory.

With reports from Jack Perry

marsenau@projo.com