When Lautenberg held a news conference last month to discuss the energy problem, Zimmer's team was there with a video camera, and later put footage of Lautenberg's stumbling for words into a Web ad titled "Empty Rhetoric."

When Zimmer and GOP State Sen. Thomas H. Kean Jr. called for summer debates with Lautenberg, and Lautenberg declined, the senator's spokeswoman called the two Republicans "Bush clones."

Though politicians don't traditionally begin rigorous campaigning until after Labor Day, Zimmer has been aggressive since the June 3 primary. He said his campaign was "getting started as early as we can. I think it's important that we engage in a real dialogue."

He has a lot of work ahead of him. The first two independent polls in the race suggest that Zimmer needs to reintroduce himself to voters. He served three terms in Congress in the 1990s, but 44 percent of respondents to the most recent of the two polls said they did not know who he was and an additional 29 percent said they had no opinion of him.

In that poll, conducted by Fairleigh Dickinson University, Lautenberg was leading Zimmer by 45 percent to 28 percent. The poll of 589 registered voters was conducted between June 17 and 22 and has a margin of error of plus or minus 4 percentage points.

Lautenberg's campaign said Lautenberg would debate Zimmer in the fall. In the meantime, the Hall Institute of Public Policy began its "virtual debate" between the campaigns Thursday, with both making opening statements. The debates are at http://www.hallnj.org/virtualdebate.

Zimmer said that while he commends the Hall Institute for hosting the virtual debate, "I wish we could share a platform so we could do it more coherently and in a way that benefits the public."

Lautenberg, taking time off this weekend to be with his family, has been spending the early days of the election campaign leveraging his incumbency by announcing his votes on bills and federal funding for state projects.

He's had a handful of appearances in New Jersey, including one where he and Newark Mayor Cory Booker announced $2.9 million in federal funding for a city park.

Zimmer, zig-zagging around the state this weekend to campaign at July Fourth events, has been trying to show where he differs with Lautenberg on issues.

He criticized Lautenberg for voting against cuts to federal gasoline taxes. A fiscal conservative, Zimmer argues that Lautenberg supports higher gas prices because he voted against the federal tax cuts.

Lautenberg's campaign readily acknowledges that he supports taxes that go into federally funded transportation projects around the state, including work on I-295 and the Garden State Parkway, and an array of bridges. His campaign said some votes were parts of bills that helped balance the federal budget, fund mass transit projects or extend the gas tax. He is a co-author of a pending bill that would tax oil companies' windfall profits and protect consumers from any price gauging at the pumps.

One issue the candidates seem to agree on is oil drilling off the New Jersey coast. When presumptive GOP presidential nominee John McCain proposed lifting the ban on offshore drilling, Zimmer quickly distanced himself from McCain's position.

Zimmer pointed out that when he was in Congress between 1991 and 1997, he introduced legislation that would protect New Jersey from offshore drilling. In a statement, he said he was "strongly against any drilling or exploration off the New Jersey coast or in any area that poses a risk to our beaches."