NEW YORK, March 3 /PRNewswire/ -- Former New York City Mayor Rudy Giuliani is the leading Republican candidate for the 2008 nomination, surging ahead of Sen. John McCain and former Massachusetts Gov. Mitt Romney, the latest Newsweek Poll shows. And in various potential match-ups for the election, top candidates polled very closely among registered voters. When asked about the race for the Republican Party's nomination, among registered Republicans, in a head-to-head contest, Giuliani tops McCain, 59-to 34 percent, the poll shows. In the January 25-25 Newsweek Poll, Giuliani's lead over McCain was four points (48% to 44%), a statistical tie with the four-point margin of error. And if the choice were between Giuliani and Romney, 70 percent say they'd choose Giuliani; 20 percent would choose Romney. If the choice were between McCain and Romney, 59 percent say they'd like to see McCain nominated; 26 percent say Romney. In various potential match-ups for the 2008 presidential election, Giuliani polled to virtual ties against some of the Democratic candidates among registered voters. For Democrat Hillary Clinton versus Giuliani, Giuliani beats Clinton 47 to 46 percent; against former Sen. John Edwards, Giuliani gets 47 percent v. 45 percent for Edwards. When pitted against Illinois Sen. Barack Obama, the gap opens: 48 percent for Giuliani v. 43 percent for Obama. The margin of error for this poll is plus or minus 3 percentage points. And 82 percent of registered Republicans say a candidate's marital history is not an important consideration for them. Giuliani has been married three times and 75 percent of registered Republicans, and 74 percent of social conservatives, say that doesn't matter to them when considering whether or not to support him for the presidential nomination. In a match-up of Clinton v. McCain, Clinton leads McCain 47- to 46 percent among registered voters. Obama tops McCain, 45-to 43 percent, and Edwards beats McCain, 48- to 43 percent, the poll shows. In a match-up of Clinton v. Romney, Clinton wins 53-to 38 percent among registered voters. Obama beats Romney, 54- to 34 percent and Edwards beats Romney, 58- to 30 percent, the poll shows. When asked about the race for the Democratic Party's nomination, if the choice were between Clinton and Obama, 52 percent of registered Democrats say they'd like to see Clinton nominated; 38 percent say Obama. Obama has gained slightly against Clinton since the January 24-25 Newsweek Poll, when Clinton was ahead 55- 35 percent. If the choice were between Clinton or Edwards, 63 percent choose Clinton v. 32 percent for Edwards. If the choice for the nomination were between Obama and Edwards, 49 percent say they'd choose Obama and 42 percent would choose Edwards, the poll shows. In deciding which Republican presidential candidate to support in 2008, 20 percent of registered Republicans say the war in Iraq is most important to them, followed by the economy (18%), issues like abortion, guns and same-sex marriage (14%) taxes and government spending (12%) health care (12%) and terrorism (11%). Still, most registered Republicans are not familiar with Giuliani's positions on key social issues: 34 percent of all Republican voters polled and 38 percent of social conservatives are aware he is pro-choice on abortion. And 51 percent of all Republican voters and 49 percent of social conservatives aren't sure where he stands on the issue. On gun control, just 17 percent of all Republican voters polled and 19 percent of social conservatives are aware he's a supporter of gun control. Sixty-seven percent of Republican voters polled (66% of social conservatives) aren't sure of his stand. And 16 percent of all Republican voters polled and 15 percent of social conservatives are aware that Giuliani opposes a constitutional amendment that would ban same-sex marriage; (70% overall and 72% of social conservatives aren't aware of his position). When asked about whether Giuliani's views on these same issues would be enough to prevent them from supporting him, few registered Republicans voters said it would. When told Giuliani supports Roe v. Wade, 29 percent of all Republican voters polled and 40 percent of social conservatives say it would make them less likely to support him. On Giuliani's opposition to an amendment that bans same-sex marriage, 25 percent of all Republican voters polled and 32 percent of social conservatives say that would make them less likely to support him. And on Giuliani's support of new laws requiring all gun owners in the U.S. to be licensed, 20 percent of all Republican voters polled and 22 percent of social conservatives say it would make them less likely to support him. President Bush's job-approval rating increased one point from the January 24-25 Newsweek Poll to 31 percent, the current poll shows. Just 27 percent approve of the way Bush is handling the situation in Iraq and 43 percent approve of Bush's handling of terrorism and homeland security; 50 percent disapprove. And 51 percent disapprove of the way Dick Cheney is handling his job as vice president. This poll is part of the March 12 issue of Newsweek (on newsstands Monday, March 5). For this Newsweek Poll, Princeton Survey Research Associates interviewed 1,202 adults, aged 18 and older on February 28-March 1, 2007. The margin of error is plus or minus three percentage points.