PRINCETON, NJ -- The most recent USA Today/Gallup poll finds Sen. Hillary Clinton extending her already sizable lead over Barack Obama for Democrats' 2008 presidential nomination preference. Half of Democrats say they are most likely to support her for the nomination, and her 29-point lead over Sen. Barack Obama is the largest she has held to date. Additionally, a majority of Clinton supporters say they are certain to support her for the presidential nomination, and nearly two-thirds of Democrats say they would vote for her enthusiastically in November 2008 if she is indeed the party's nominee. Leads greater than 20 percentage points have been rare in past Democratic campaigns, but historically those who have enjoyed such a large lead in Gallup Polls this late in the year won the nomination the following year.

Most Recent Democratic Results

The Oct. 12-14, 2007 update finds 50% of Democrats (including independents who lean to the Democratic Party) supporting Clinton for the nomination, her best showing so far. Obama is a distant second at 21%, followed by former Sen. John Edwards at 13%. The five other active presidential candidates are supported by 4% or less of Democrats.

Clinton has never trailed at any point in the campaign, and has led Obama by at least 20 percentage points since August. Her lead has expanded from 21 points in the previous poll to 29 points as a result of a slight increase in support for her (from 47% to 50%) and a slight dip in support for Obama (from 26% to 21%). Both changes are within the polls' margins of sampling error, however.

Clinton's Lead in Historical Perspective

Since the 1972 campaign -- when the power to choose the party nominees was shifted from national convention delegates to voters in state primaries and caucuses -- Democrats have rarely had a front-runner as dominant as Clinton. In four of eight contested nomination campaigns from 1972 to 2004, no candidate had a lead of 20 points in a Gallup Poll at any point during the year prior to the election. In two other campaigns, this occurred just once during that time. Only in 1979 (Sen. Ted Kennedy) and 1999 (former Vice President Al Gore) were front-runners able to sustain a lead of that magnitude for several polls.

Number of Gallup Democratic Nomination Polls Showing

Leading Candidate With Lead of 20 Points or Greater,

Year Before the Presidential Election Year Number of Polls Showing

Democratic Nomination Leader With 20-point lead or Greater Total Number of Gallup

Democratic Nomination Polls

Taken During Year 1971 0 7 1975 0 5 1979 3 4 1983 1 9 1987 1 8 1991 0 5 1999 12 15 1995 0 0* 2003 0 19 Total 17 72 * Bill Clinton was uncontested for the 1996 Democratic nomination.

As the table indicates, the majority of the historical 20-point leads occurred in 1999, when then-Vice President Gore was only challenged by former Sen. Bill Bradley for the 2000 Democratic nomination. So far, Clinton has held a lead of 20 points or more in 8 of 18 Gallup polls taken this year, including the last 6 polls.

Clinton is just the fifth Democratic presidential candidate since 1972 to hold a 20-point lead at any point in the year prior to the election. The others were Kennedy in June and July 1979, former Vice President Walter Mondale in November 1983, former Sen. Gary Hart in April 1987, and Gore for most of 1999.

Polls Where Leading Democratic Candidate for Nomination in Gallup Poll Had

20-Point Lead or Greater Date(s) Leading

Candidate Second Place

Candidate Size of Lead

(in pctg points) 1979 June 1-4 Kennedy (52%) Carter (17%) 35 1979 June 22-25 Kennedy (54%) Carter (22%) 32 1979 July 13-16 Kennedy (53%) Carter (21%) 32 1983 Nov 18-21 Mondale (47%) Glenn (19%) 28 1987 Apr 10-13 Hart (46%) Jackson (18%) 28 1999 Jan-Sep (9 polls) Gore (avg 59%) Bradley (avg 26%) 33 (avg) 1999 Oct 21-24 Gore (57%) Bradley (32%) 25 1999 Nov 4-7 Gore (58%) Bradley (33%) 25 1999 Dec 9-12 Gore (57%) Bradley (36%) 21 2007 Feb 9-11 Clinton (48%) Obama (23%) 25 2007 Apr 2-5 Clinton (43%) Obama (19%) 24 2007 Aug-Oct 7 (5 polls) Clinton (avg 47%) Obama (avg 25%) 22 (avg) 2007 Oct 10-12 Clinton (50%) Obama (21%) 29

Kennedy and Hart ultimately lost their nomination bids, but their large leads came much earlier in the campaigns. Kennedy's candidacy lost its steam when Jimmy Carter's popularity surged in late 1979 following the Iran hostage crisis and the Soviet invasion of Afghanistan. Hart's 20-point lead occurred in the last poll taken before he suspended his campaign after the press was able to confirm rumors he was having an extramarital affair.

Mondale and Gore, who like Clinton held their large leads much later in the campaign, both went on to win the Democratic presidential nomination. Moreover, Mondale and Gore saw their leads expand between the start of the election year and the Iowa Caucuses. Both then won the Iowa caucuses, though Mondale would subsequently lose the New Hampshire primary to Hart and see his lead disappear. Mondale recovered and had the nomination well in hand by April. Gore won the 2000 New Hampshire primary over Bradley and easily won the nomination.

Clinton is also just the third Democratic presidential candidate to have reached 50% support on Gallup's national ballot in the year prior to the election, joining Kennedy in 1979 and Gore in 1999. Gore's long run of support in excess of 50% is partly attributable to the fact that he had just one challenger for the nomination.

Large leads and support in excess of 50% have been much more common on the Republican side. In fact, every Republican presidential nominee since 1972 has led his challengers by 20 or more points at some point in the year prior to the election. All but Gerald Ford in 1975 and George H.W. Bush in 1987 reached 50% support on Gallup's national ballot the year before the election. Giuliani has yet to reach 50% (his high was 49% in March), but he has led the field of Republican challengers by better than 20 points in March and April of this year. However, his support has declined since that time and his lead has averaged just 12 points.

Implications

By now, it is obvious that Clinton is extremely well-positioned to win the 2008 Democratic presidential nomination. Her status as the front-runner seems to be strengthening at an opportune time with the Iowa Caucuses less than three months away. It is not beyond the realm of possibility that she could stumble and not win the nomination as did Kennedy and Hart, but those cases occurred under rather extreme circumstances. Also, those candidates held their large leads long before any votes were cast. Because of her large lead this close to the first official contest, one would expect the Clinton campaign to "play it safe" and not take the sort of risks that could derail her campaign. Indeed, the perception is that she is already "moving toward the center" by taking more moderate positions on issues that Democratic primary voters may not necessarily endorse, but that may position her better for the general election campaign against the Republican. At the same time, her chief rivals Obama and Edwards find themselves in a position where they may have no choice but to step up their attacks on her in an effort to weaken her standing.

Survey Methods

These results are based on telephone interviews with a randomly selected national sample of 500 Democrats and Democratic-leaning independents, aged 18 and older, conducted Oct. 12-14, 2007. For results based on this sample, one can say with 95% confidence that the maximum error attributable to sampling and other random effects is ±5 percentage points.

In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.