Lisa McCormick's surprisingly strong showing against U.S. Sen. Robert Menendez in Tuesday's Democratic primary begs the question: What about Bob?

McCormick, a virtual unknown who did not report spending any money on the race, received the support of almost 4 in 10 Democratic voters.

While Menendez, D-N.J., was never seriously threatened with losing his party's nomination for another Senate term, his performance wasn't a good sign coming on the heels of his Senate Ethics Committee admonishment and a criminal corruption trial that ended in a hung jury before the charges were dropped.

"This is closer than we expected, but only because we expect huge margins for candidates with as much party and institutional support as Senator Menendez has," said Matthew Hale, a political science professor at Seton Hall University. "In most places, a 60/40 win is considered a drubbing."

Not in this place.

"Bob Menendez performed terribly against a totally unknown challenger," Republican National Committee spokesman Michael Ahrens said. "Even a significant number of New Jersey Democrats made it clear they don't want him re-elected."

Former Celgene Corp. executive Bob Hugin won the Republican primary, 75 percent to 25 percent, over construction company owner Brian Goldberg. Menendez was expected to compile a similar margin against McCormick, a community newspaper publisher.

"I thought maybe she'd get 25 percent of the vote as a protest vote against Menendez," said Patrick Murray, director of the Monmouth University Polling Institute. "That's not unusual. Forty percent is what you'd expect to see in a contested primary."

One solace for Menendez is that almost 200,000 more Democrats than Republicans went to the polls. In fact, McCormick's 157,000 votes were just 10,000 shy of Hugin's total.

"Bob Hugin just spent millions of dollars on attack ads against Senator Menendez, yet tonight, tens of thousands of more Democrats than Republicans came out to vote for Senator Menendez than for Bob Hugin," Menendez campaign chairman Mike Soliman said.

"We haven't spent on TV yet because every dollar saved during a primary will go much farther during the general election, and we can't allow Bob Hugin to go to Congress and cast a vote for Donald Trump against New Jersey values."

Political analysts said McCormick's candidacy allowed progressive Democrats to cast protest votes in the primary, where it will not jeopardize a Democratic Senate seat but will make their voices heard.

Because of an energized Democratic base, people voting now used to sit home in off-year elections. That meant Menendez faced a different electorate than the one he was used to, Democratic consultant Glenn Totten said.

"This is a genuine mood for new blood and no one is immune from that tidal wave," Totten said. "There is an urgency to Democratic voters. Part of that urgency is a Democratic Party that is responsive to their concerns."

Menendez's ethical problems played a role, Hale said. The Senate Ethics Committee "severely admonished" him in April for intervening with federal agencies on behalf of Dr. Salomon Melgen while accepting gifts and trips from his friend and campaign donor.

"All of the news about Menendez was bad," Hale said. "The ethics committee's decision was right in the middle of the race, so I think all of those things combined to make it a lot closer than we expected."

In the end, not too many McCormick voters will cross party lines, said Nathan Gonzales, editor and publisher of Inside Elections, which rates Menendez as a strong favorite for re-election.

"I'm not convinced too many Democrats are so upset or disappointed with Menendez that they'll vote for a Republican in November," Gonzales said.

Staff writer Matt Arco contributed to this report.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.