Two others mulling 2008 presidential bids, Democratic Sen. Barack Obama and Republican Sen. John McCain, were second and third, respectively, in the poll released Monday by Quinnipiac University.
Quinnipiac's "thermometer reading," taken the week after the Nov. 7 election, asked voters to rate their feelings for 20 leaders on a scale of 0 to 100.
Giuliani, a Republican, scored the highest at 64.2. Obama and McCain, who are also considering a 2008 campaign, finished next at 58.8 and 57.7.
"As we enter the presidential campaign of 2008, Giuliani and McCain are in enviable positions," said Peter Brown, assistant poll director. "They are well-regarded and most Americans are quite familiar with them. Obama's showing is impressive, but four in 10 Americans still don't know enough about him to have an opinion."
Secretary of State Condoleezza Rice was fourth in the poll, far ahead of her boss, President Bush, who was the 15th most popular national leader. Mr. Bush finished just behind the man he defeated in the 2000 presidential race, former Vice President Al Gore.
Former President Bill Clinton finished fifth in the poll, while his wife, New York Sen. Hillary Rodham Clinton was ninth with a score of 49. Massachusetts Sen. John Kerry, the 2004 Democratic nominee who was roundly criticized before the election for suggesting that students who don't study could end up stuck in Iraq, came in last at 39.6.
Kerry later apologized for what he said was a botched joke.
Connecticut Sen. Joseph Lieberman, who lost the Democratic primary before winning re-election as an independent, ranked sixth with a score of 52.7.
Democratic Rep. Nancy Pelosi, in line to become the next House Speaker, improved her standing, moving from last to 12th in a few weeks. The next Senate Majority leader, Democrat Harry Reid, was 19th.
The telephone poll was conducted from Nov. 13-19. Quinnipiac surveyed 1,623 registered voters nationwide and the poll has a sampling error margin of plus or minus 2.4 percentage points.
Here's how they finished: