Sen. Barbara Boxer has been locked in a tight re-election race with former HP CEO Carly Fiorina for months, and, according to the latest polling from Field Research, things are looking modestly up.

After a string of polls that showed Boxer leading in the lower single digits (and a couple that showed Fiorina ahead), Boxer leads 47 - 41 percent according to Field, while SurveyUSA's automated polling shows her up 49 - 46 percent.

But this race is still extremely tight, and not all of the numbers are encouraging for Boxer. Here's why.

A healthy chunk of California's electorate is still undecided: Field reports that 12 percent haven't made up their minds. (SurveyUSA shows this figure at 2 percent, but, for whatever reason, SurveyUSA's methodology yields lower than average undecided numbers. For instance, only 4 percent of respondents in Kansas said they were undecided on the race for Kansas' next secretary of state.) Given Field's +/- 4.1 percent margin of error, that means Boxer could be ahead by as much as 10 percent or as little as two percent.

Voters don't necessarily like either candidate, as both have higher unfavorable ratings than favorable, according to Field. For Boxer, 45 percent like her, and 48 percent don't; for Fiorina, 34 percent like her, and 38 percent don't.

Another point about this: when Field took its survey, which was conducted September 14 - 21, Boxer was running statewide general-election ads. Fiorina just launched her statewide general-election TV campaign (after running a primary campaign, mind you), yesterday.