The term “no-man’s land” evolved from World War I, when the opposing armies burrowed into trenches and land between the lines became a killing field.

It’s an apt term for contemporary American politics, which have become so polarized and stalemated that anyone who tries to occupy the middle ground is targeted by one side, or both.

Such as Democratic U.S. Sen. Dianne Feinstein.

WeeklyWalters: your Friday newsletter for all of Dan's columns.

Since her first election to U.S. Senate in 1992, the former San Francisco mayor has easily turned back Republican efforts to unseat her, largely because of her centrist politics.

Now 84, she gave every indication that she didn’t really want to run for another six-year term.

However, the Senate’s Democratic leaders, worried that her retirement would ignite a very expensive Senate race in California that would divert campaign money they needed in other states, persuaded her to make the run. Instead of the cakewalk they assumed, however, Feinstein finds herself taking heavy fire from the left wing of her own party.

Republicans may have finally given up hope of claiming her seat, but the left-wingers, who have never liked her pragmatic approach, are incensed by her seeming unwillingness to fully embrace “the resistance” to President Donald Trump—even, at one point, suggesting that he could evolve into a good president.

Enter Kevin de León, the three-decade-younger former president pro tem of the state Senate, who has made resistance to Trump a personal crusade and who is being forced to give up his Senate seat due to term limits. He launched a bid to deny Feinstein another term.

The Democrats’ left wing, popularly dubbed “Berniecrats,” dominated last month’s state Democratic convention and clearly preferred de León over Feinstein, voting 54 percent to 37 percent for the challenger.

“I’ve never been fooled into believing that Donald Trump can be a good president,” de León said in one of several jabs at Feinstein.

Feinstein made an unfortunate gaffe as the auditorium’s music was turned up to signal that her allotted time at the podium had expired.

“I guess my time is up,” she said. “Your time is up,” de León’s more numerous cheerleaders began chanting.

They may think—or at least hope—that’s true.

However, while Feinstein has shifted leftward somewhat in response to the de León challenge, at least in her public statements, a new poll from the Pubic Policy Institute of California indicates that she’s still fairly popular in the broader electorate.

Forty-five percent of all adults and 54 percent of likely voters approve of Feinstein’s performance in the Senate, somewhat higher than her fellow Democratic senator, Kamala Harris, can claim.

Furthermore, Feinstein holds a 42 percent to 16 percent lead over de León among likely voters and has much, much more campaign money to spend.

Under the state’s old electoral system, a lead of that magnitude just three months before the primary election would be definitive. Feinstein, as she had previously, would win the Democratic nomination and easily defeat a token GOP challenger.

However, under the top-two primary system, and with no substantial Republican on the June ballot, it’s very likely that Feinstein and de León will face each other again in November.

He’s got a lot of ground to make up but will likely have five more months to do it. With polarization becoming ever stronger, Feinstein will still be dodging bullets in no-man’s land.