Updated

Ever since she was elected to the U.S. Senate 18 years ago, Barbara Boxer has faced little competition in winning another term. But this year, it won't be that easy.

Polls indicate that the California Democrat may be about to meet her match – who will be determined in a June primary. According to one poll, Boxer is neck and neck with all three of the Republicans who hope to run against her in the general election: former Rep. Tom Campbell, former Hewlett-Packard CEO Carly Fiorina and state Assemblyman Chuck DeVore.

In the latest Rasmussen Reports from last month, Boxer led Campbell 43 to 41 percent and was beating Fiorina and DeVore 46 to 40 percent.

"She's in for tough sledding and she's got lots of prominent Republicans ready to go after her," political analyst Juan Williams told Fox News. "So what I sense there is that she knows the economy in California and especially the budget, government budget, state budgets have been a huge issue and there's a lot of discontent, particularly with her."

Boxer is hardly the only congressional Democrat facing an uphill battle in November. Many political analysts are predicting significant GOP gains in the House and the Senate in a toxic environment for incumbents in which the recent health care law and the fragile economy loom large and could be the deciding factors.

Democrats control 57 seats in the Senate, with two independents caucusing with them. Republicans need 10 net victories to regain control.

In the House, where Democrats have 253 seats, Republicans need 41 net pickups to win back the chamber.

"This is already going to be the biggest election since '94," Larry Sabato, director of the University of Virginia's Center for Politics, told Fox News. "What we have to figure out, and we'll find out on election night, is whether it's as big or bigger."

Sabato is predicting Republicans will gain 27 seats in the House and seven seats in the Senate. He calls the Boxer race a toss-up.

On Thursday, Boxer acknowledged the tough challenge she and her fellow Democrats are facing this year.

"I really think nobody can take their seat for granted," Boxer told a local news station. "These are tough times that we're going through in America and California, and I'm not going to sugarcoat that."

Boxer said most of her campaigns have been hard for her.

She first won election to the Senate in 1992, beating conservative commentator Bruce Herschensohn in an open seat contest by nearly 5 percentage points. Ever since then, no opponent has come as close to competing with her. In 1998, she beat a former state treasurer by 10 percentage points. In 2004, she defeated a former state secretary by 20 percentage points.

"People look at my career and they think they're easy," she said. "I did win by a lot the last time. But even that was a tough campaign until the people got the message about what the choice was. And that's how I think this one is going to be."

Boxer said she's expecting a tough race but believes she will prevail.

"At the end of the day, the people I really believe will say Barbara Boxer stands in my corner, fights for me, fights for my jobs. And that's what they need right now."

Boxer rejected the notion, one most recently raised by Karl Rove, that she is vulnerable because she is consistently polling below 50 percent.

"I would say right now, if you look in California, most of the office holders are below 50 percent because people are grumpy and they have a right to be grumpy. But that doesn't say anything. I've won 10 elections and in every one of those, I was below 50 percent. This is a big state. You've got to get your message out. And when people hear that I'm on their side, fighting for their jobs, I think they'll choose me."