Sen. Barbara Boxer, who has taken heat in recent months for clashes at Senate hearings, is facing a potentially tough election challenge from prominent businesswoman Carly Fiorina, who is within striking distance in a recent poll.

Fiorina, a former Hewlett-Packard CEO and top economic adviser to John McCain's presidential campaign, hasn't said yet whether she'll throw her hat in the ring against Boxer for the California Democrat's Senate seat next year. But it already could be shaping up to up be one of the most closely watched Senate contests.

A Rasmussen Reports telephone survey released July 24 shows that Fiorina is trailing by only 4 percentage points behind in a hypothetical head-to-head with the three-term incumbent. The poll put Boxer's support in such a face-off at only 45 percent, with  7 percent of survey respondents saying they're undecided.

In March, the same month Fiorina told reports she was "seriously considering" launching a bid, Boxer led her potential challenger by 9 percentage points with a 47 percent support in the Rasmussen poll. The poll has a sampling error of +/- 4.5 percentage points.

"Any incumbent who polls below 50 percent early in a campaign is considered potentially vulnerable," the polling firm said in a report accompanying the poll results. "However, a Democrat running in a heavily Democratic state like California is often able to overcome weak poll numbers."

But Fiorina's personal wealth -- HP provided her with a $21 million severance package -- ensures that she could carry out a full-scale attack. And Boxer has drawn negative press in recent weeks for two contentious exchanges, with a military officer and a black business leader.

Harry C. Alford, the president and CEO of the National Black Chamber of Commerce, accused Boxer this month of racially condescending to him during an Environment and Public Works Committee hearing. Alford, whose testimony Republicans had sought to oppose a climate change bill working its way through Congress, took offense to Boxer quoting supporting statements from the NAACP and 100 Black Men group.

"I'm the National Black Chamber of Commerce and you're trying to put up some other black group to pit against me," he angrily told Boxer. "As an African-American and a veteran of this country, I take offense to that."

Boxer defended herself by saying she believes statements by the NAACP and 100 Black Men, who affirm the threat of global warming, are relevant and show the diversity of support behind the climate change bill, which narrowly passed in the House.

In June, Boxer rebuked an Army Brigadier general for calling her "ma'am."

"You know, do me a favor," an irritated Boxer told Brig. Gen. Michael Walsh, with the U.S. Army Corps of Engineers. "Could you say senator instead of ma'am? ... It's just a thing, I worked so hard to get that title, so I'd appreciate it."

Boxer later said she had a "friendly" conversation with Walsh after the exchange and defied calls for her to apologize publicly.