The race for the top Republican spot among 2008 White House hopefuls is heating up as likely contender former Tennessee Sen. Fred Thompson moved into second place, tying Arizona Sen. John McCain in the latest poll.

Former New York City Mayor Rudy Giuliani still leads Republicans if a nationwide primary were held today, with 27 percent backing Giuliani and Thompson and McCain following behind with 15 percent apiece. Former Massachusetts Gov. Mitt Romney got 10 percent, according to the Quinnipiac University poll conducted June 5-11.

Click here to read the Quinnipiac poll.

Thompson, a former senator from Tennessee and an actor on NBC's "Law & Order," inched closer to jumping into the race officially, telling "The Tonight Show" host Jay Leno on Tuesday night that "I've never craved the job of president, but I want to do some things that only a president can do.

"I'm at a stage of my life now when I think about my country, I think about the kind of country my kids are going to grow up in," Thompson told Leno.

While Giuliani is well ahead of the GOP pack, he no longer finds himself as the top candidate for president. Three Democratic hopefuls have closed in on or passed his lead, according to the poll.

In a mock head-to-head, New York Sen. Hillary Clinton got 45 percent to Giuliani's 44 percent, Illinois Sen. Barack Obama tied Giuliani with 42 percent and former Vice President Al Gore, who also is not in the race, got 45 percent to Giuliani's 43 percent.

Giuliani had a 49 percent to 40 percent lead over Clinton in a May 3 poll, where he also bested Obama and Gore.
“Mayor Rudolph Giuliani’s support erodes against the leading Democrats, but he holds steady as the frontrunner on the Republican side,” said Maurice Carroll, director of the Quinnipiac University Polling Institute.
Clinton leads the field of Democratic hopefuls with 35 percent. Obama received 21 percent and Gore got 18 percent.
Quinnipiac University surveyed 1,711 American voters for the poll, which had a margin of error of plus or minus 2.4 percent.

On Tuesday, the latest Rasmussen Reports favorability poll put both Giuliani and Thompson in the leading spot for Republican White House contenders.

Twenty-four percent of Republican voters support both Giuliani and Thompson. Last week, the former New York City mayor led Thompson by 6 percentage points, according to the poll of 633 likely Republican primary voters.