Cory Booker, the celebrity mayor of Newark, N.J., was expected to cruise to victory in the special election to fill the U.S. Senate seat of the late Frank Lautenberg. But just a week before voters go to the polls, he's facing a surprisingly strong challenge from Tea Party favorite Steve Lonegan.

The race was supposed to be a mismatch: Booker, the Democrat, and his 1.4 million Twitter followers versus the Republican former mayor of Bogota, N.J. — population 8,000.

But no one told Lonegan.

In their first debate, Lonegan chided Booker for spending more time tweeting and traveling than solving Newark's problems.

"What New Jersey needs, sir, is a leader, not a tweeter," Lonegan said. "We need somebody who's going to be there to govern, who's going to be there to do the job — not be running around the country on speaking tours and getting speaking fees."

It's true that Booker has made a lot of money from his speaking engagements — more than $1 million in the past five years. But Booker says he's raised even more in philanthropic donations.

"Please understand: I have traveled around the country. But when I do, I actually bring back resources for Newark, New Jersey," he said. "We set a record with over $400 million of new philanthropy in our city."

Booker has been on the defensive lately. He has had to answer questions about his personal investments, a made-up character he used in stump speeches — even friendly Twitter messages with a stripper in Oregon.

Booker's relaxed campaign schedule hasn't helped him either, says Brigid Harrison, who teaches political science at Montclair State University.

"We've seen this kind of Rose Garden campaign strategy where he doesn't seem to be out and about and campaigning a whole lot," she says. "And he's really kind of played this off as if he's already won the election."

Booker is still leading, but one recent poll showed Lonegan within a dozen points heading in to the Oct. 16 election. This week, the Booker campaign responded with a more vigorous schedule — and sharper attacks.

"My opponent right now represents the Tea Party in New Jersey," Booker said at a forum in the North Jersey suburb of Whippany, "and has those extreme views that to me are what make everything that's wrong with Washington worse."

Lonegan doesn't deny that he's a conservative. He ran the New Jersey chapter of Americans for Prosperity, a group tied to the Koch brothers. Lonegan says he believes in Republican efforts to fight the Affordable Care Act.

"There are times for compromise, and there's times for not compromising," he says. "In this current government shutdown today, I believe that Obamacare is a trainwreck."

That message seems to be connecting with core Republican voters like Joe Eckel.

"I've known Steve for a quite a while," Eckel says. "I think he's a stand-up guy. And he's fiscally responsible."

But Lonegan's ideas on the role of government and social issues like abortion may be too extreme for many New Jersey voters, who tend to support centrist Republicans like Gov. Chris Christie.

Steve Newmark of Florham Park, who describes himself as an independent, says he "can't think of a better guy" than Christie. But when it comes to Lonegan, Newmark says: "I tend to think he's a little too to the right for me."

New Jersey hasn't elected a Republican senator in 40 years. That should reassure Booker's supporters. But voter Lew Schwarz is taking nothing for granted in a special election on a Wednesday in the middle of October.

"Booker has run a lackluster campaign," Schwarz says. "And this special election is like a primary, when you can never be absolutely certain who's going to win. Because if you don't get a big vote out for your person, you may get a nasty surprise."

A win for Lonegan next week would be a nasty surprise for Democrats in the Senate, who look forward to recovering the seat they lost when Lautenberg died in June. Republican Jeff Chiesa, formerly New Jersey's attorney general, was appointed by Christie to serve until the special election.

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