I can't say whether or not he is doing this intentionally, but I
think you could actually make the counterintuitive argument that
Barr can steal more votes from McCain by attacking Obama. The way I
see it, Barr is a threat because there are still conservatives out
there who have a hard time stomaching McCain, but would vote for
him as the lesser of two evils. Barr could peel away these voters
by convincing them that they have another anti-Obama option. By
attacking Obama (especially as he did the other day on the Second
Ammendment) Barr reinforces that he is a conservative more than he
does if he's always quoted going after McCain. Furthermore, one of
the concerns conservatives have in this election is that McCain's
committment to running a "respectful" campaign will translate into
him going soft on Obama, and provide further evidence that he's
much nicer to Democrats than his fellow Republicans. If Barr is
willing to take his gloves off in going after Obama, it could make
McCain look like Democrat lite.