Kevin Drum thinks so:

Bottom line: Ron Paul is not merely a "flawed messenger" for these views. He's an absolutely toxic, far-right, crackpot messenger for these views. This is, granted, not Mussolini-made-the-trains-run-on-time levels of toxic, but still: if you truly support civil liberties at home and non-interventionism abroad, you should run, not walk, as fast as you can to keep your distance from Ron Paul. He's not the first or only person opposed to pre-emptive wars, after all, and his occasional denouncements of interventionism are hardly making this a hot topic of conversation among the masses. In fact, to the extent that his foreign policy views aren't simply being ignored, I'd guess that the only thing he's accomplishing is to make non-interventionism even more of a fringe view in American politics than it already is. Crackpots don't make good messengers.

And yet many, many voters who watch and listen to the man do not see a crackpot. They see the only person in public life prepared to tell the truth: that America cannot afford its current military-industrial complex and entitlement state; and that America's lurch after 9/11 toward authoritarianism and empire has been disastrous for our interests and liberties. Who else, one wonders, would Kevin want people to vote for if they want a real shift away from aggression abroad, an imperial presidency at home and a drug war whose victims count in the millions. Obama? The man whose response to marijuana legalization was to laugh out loud? Who just signed into law the right of a president to seize any citizen at will and detain him or her indefinitely without trial? The president who launched a war in Libya and refused even to ask for Congress's approval after two months? Who else on the right? Dan Drezner has a somewhat different critique:

Ron Paul is great at affecting the marketplace of ideas. He would be worse than Newt Gingrich if he actually became  president, however.  The great presidents — Washington, Lincoln, FDR — knew when to compromise and when to stand firm, when to lead public opinion and when to follow it. They were, in other words, great politicians. The presidents who simply knew they were right on everything and resisted compromise — Jackson, Wilson, Bush 43 — tended towards the disastrous.  Paul would be part of the latter group. 

So if Ron Paul wants to influence the debate, that's good. He raises important questions about important issues. He's also wrong about some really important issues and therefore should be kept away from the presidency. 

Look what an impact Paul has made on the GOP in the last five years. But, yes, as I wrote in my withdrawn endorsement, he does have all the problems of a total ideologue. He would be a president primarily of vetoes – forcing all sorts of strange alliances in the Congress to overturn them. But I don't see why he, more than, say, Gingrich, should be "kept away" from the presidency. He's one of the least volatile temperaments among these candidates, and has strong competition for nuttiness. He's not the one advocating Congress's right to haul judges before them and abolish whole circuits. He's not for mining on the moon. Or for "doubling Gitmo". Or for criminalizing all abortion in every state. Or for "curing" gays as a business.