TRENTON, N.J. – President Bush, in his most dramatic move in the polls to date, has climbed into a tie position with Senator Kerry in a state that was once considered an impregnable Democratic stronghold, New Jersey, according to a new poll of likely and undecided voters in the Garden State.

According to a Quinnipiac University poll reported by the Associated Press, Messrs. Bush and Kerry are tied among likely New Jersey voters for the state’s 15 electoral votes.

Forty-eight percent of the likely and undecided voters leaning toward a candidate polled by Quinnipiac University said they support the president or the Democrat. Two percent favored Ralph Nader.

Mr. Kerry was slightly ahead in the same survey among Garden State registered voters polled, 47% to 43%. The Massachusetts senator had a 10-point lead among registered voters polled by Quinnipiac in August before the Republican National Convention.

Mr. Kerry lost a double-digit lead over Mr. Bush in New Jersey and was nearly tied with the GOP incumbent in a Star-Ledger/Eagleton-Rutgers Poll released earlier this month. Mr. Bush, coming off his party’s national convention, slashed Mr. Kerry’s lead among Garden State voters to four percentage points.

This represents a dramatic drop for Mr. Kerry, who held a commanding 20-point lead over Mr. Bush among likely Garden State voters in a Star-Ledger survey after the Democratic National Convention in July.

New Jersey voters questioned by Quinnipiac said Mr. Bush would do a better job on terrorism, which respondents said was the most important issue in the presidential race, according to the Associated Press. Mr. Kerry got higher marks for handling the economy. By a 55 to 40% margin, Garden State respondents said it was wrong for America to go to war in Iraq.

When asked if the scandal surrounding Governor McGreevey’s resignation last month had affected Mr. Kerry’s support in New Jersey, Senator Corzine said “it had some impact on voters’ confidence about the Democratic Party in general, and so it probably has had some impact.”

“I don’t think any of the kinds of things that have gone on are helpful to the overall ticket,” Mr. Corzine said during a conference call yesterday, the Associated Press reported. “I don’t think they will be the overwhelming decision factor when we get to November.” Mr. Corzine is widely seen as a frontrunner for the Democratic nomination for governor next year.

The presence of Mr. Nader on the New Jersey ballot could ultimately prove decisive, said Maurice Carroll, director of the Quinnipiac University Polling Institute.

“Nader’s vote is minuscule, but when we winnow down the list to likely voters, it’s clear that Nader’s 2% could be the key in New Jersey,” Mr. Carroll said, according to the Associated Press.

The survey of 943 registered voters had a sampling error of 3.2 percentage points. Among 672 likely voters, the sampling error was 3.8 percentage points.

Since Mr. McGreevey announced that he would be resigning because of an extramarital affair with a man who had worked in a senior level in his administration, state Democrats have been embroiled in a succession struggle. The McGreevey administration has been beset by corruption scandals, with the governor’s two principal fund-raisers and his two closest aides all indicted or facing indictment. In one case, a top fund-raiser, Charles Kushner, also a major philanthropist in the Jewish community, plead guilty to witness tampering after he videotaped his brother-in-law having sex with a prostitute and sent the tape to his sister, a scandal that dwarfed Mr. McGreevey’s confession.

Republicans have made no progress in pressing their case that Mr. Mc-Greevey’s resignation should take effect at once. Instead, Mr. McGreevey will hang on until mid-November, when he will hand the state house over to the state Senate president, Richard Codey.

Meanwhile, Republicans interested in securing their party’s nomination to run against whomever the Democrats pick next year have been meeting with supporters and raising funds.

Badly divided between conservative and moderate wings, the state GOP must heal its internal rifts if it has a chance to recapture Drumthwakett.

The Quinnipiac poll indicates that Mr. Bush’s campaign themes have resonated even with voters who think the Iraq war was a mistake.

The results mean that Mr. Kerry’s campaign will have to devote resources to a state with two expensive major media markets, New York City and Philadelphia. New Jersey has trended Democrat in the last four presidential elections, and in statewide elections for U.S. senator.

The Republicans won the governorship when they ran moderates, like Tom Kean Sr. and Christine Todd Whitman.