Washington (CNN) - When is a 20 percentage point lead not so impressive?
When it's down from a 30-point lead.
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With 2 1/2 months to go until the New Jersey governor's election, a new Monmouth University/Asbury Park Press Poll released Wednesday indicates that Gov. Chris Christie is crushing his Democratic challenger, state Sen. Barbara Buono, 56% to 36% among likely voters. But Christie's 20-point advantage is down from a whopping 61%-31% lead in the last Monmouth survey in mid-June.
According to the poll, the tough-talking GOP governor has the backing of 90% of Republicans and nearly two-thirds of independents, but his support among Democrats now stands at 21%, down from 36% in June.
"The trend suggests that New Jersey Democrats are coming back home. But it's not quite enough for Buono to overcome Christie's sizable advantage among independents," Monmouth University Polling Institute Director Patrick Murray said.
Christie held a 58%-30% lead over Buono in a Quinnipiac University poll conducted at the beginning of August.
Christie's trying to score an impressive re-election victory in November with the support of not only Republicans but also Democratic and independent voters. Christie's 2013 re-election bid is also increasingly seen as a testing ground or launching pad for a possible 2016 bid for the White House.
Those presidential ambitions don't come as a surprise to most Garden State voters - 19% of those questioned in the poll say they think Christie's definitely running in 2016, with six in 10 saying he's probably going to run. Among those who think Christie's definitely going to run, he's up 50%-39% over Buono.
"Convincing more voters that Governor Christie has his eyes set on the White House may narrow the gap for Buono, but is unlikely to close it," Murray added.
The Monmouth University/Asbury Park Press Poll was conducted by telephone from August 15-18 with 777 New Jersey voters likely to cast ballots in the November election. The survey's overall sampling error was plus or minus 3.5 percentage points.