WASHINGTON (CNN) -- A year and a half before the 2008 presidential election, Rudy Giuliani and Sen. John McCain are leading the Republican pack, according to a CNN/Opinion Research Corporation Poll out Monday.

Asked whom they would most likely support for the Republican nomination, 25 percent of people who identified themselves as Republicans or leaning Republican cited the former mayor of New York and 23 percent cited the senator from Arizona. (Full Poll Results [PDF] )

Former Sen. Fred Thompson of Tennessee, who has not said he is running, was cited by 13 percent; former Massachusetts Gov. Mitt Romney by 10 percent; former Speaker of the House Newt Gingrich -- who has not said he is running -- by 9 percent; former Virginia Gov. Jim Gilmore by 3 percent; former Arkansas Gov. Mike Huckabee by 2 percent, Colorado Rep. Tom Tancredo by 2 percent; former Wisconsin Gov. Tommy Thompson by 2 percent; California Rep. Duncan Hunter by 2 percent; Rep. Ron Paul of Texas by 1 percent.

The CNN Opinion Research Corporation telephone poll was carried out Friday through Sunday and included 414 registered voters who described themselves as Republicans or as independents who lean Republican. The margin of error for the poll is plus-or-minus 5 percent. (Interactive: poll results)

Full Results

Giuliani         25%
McCain           23%
F. Thompson      13%
Romney           10%
Gingrich          9%
Huckabee          3%
Brownback         2%
Tancredo          2%
Gilmore           2%
T. Thompson       1%
Paul              1% 
Hunter            1%
No opinion        8%