Former Rep. Tom Campbell (R) is within the margin of error in a hypothetical matchup with Sen. Barbara Boxer (D) in a new Research 2000 poll conducted for the liberal blog Daily Kos.

Among likely voters, the poll found Boxer leading Campbell, 47 percent to 43 percent, with 10 percent undecided. The poll, conducted March 8-10, had a margin of error of 4 points.

Looking at the two other potential Republican nominees, the poll found Boxer topping former Hewlett-Packard CEO Carly Fiorina, 49 percent to 40 percent, with 11 percent undecided. And Boxer led GOP state Assemblyman Chuck DeVore 49 percent to 39 percent, with 12 percent undecided.

In the GOP primary, Campbell led with 33 percent, followed by Fiorina at 24 percent and DeVore at 7 percent.