Strategic voting poses a challenge to the designers of any electoral system that aims to translate voter preferences into election winners. But it's also a problem for individual voters trying not to outfox themselves, as Democrats arguably did in 2004. Fearing vulnerability on national security, they nominated John Kerry, who was then attacked as a traitor AND who ran a weak campaign on other issues to boot. It's impossible to know what would have happened had someone else been the standard bearer in 2004, but it's hard to imagine that Howard Dean (the early front-runner) or John Edwards (a strong finisher) would have done much worse---and by nominating one of them, Dems would at least have voted their true preferences.
Strategery also creates difficulties for voters trying to decide whom to root for among the other party's candidates. The current Presidential primary process is a nice example.
For socially liberal Democrats, Rudy Giuliani is probably the least offensive Republican candidate. So socially liberal Democrats faced with the question of which Republican in the current field they would most like to see as President, IF a Republican were to win the election, would likely pick Giuliani. However, Giuliani would make a formidable candidate, in part BECAUSE he does not hold strongly conservative social views (and in part because, as Mayor of 9/11, he has appeal in running to become President of 9/11). So a liberal Democrat might well rather see, say, Tom Tancredo get the Republican nomination. Although, from the perspective of liberals, Tancredo would be a disastrous President, his nomination would increase the likelihood that a Democrat wins the general election, and almost any Democrat in the current field would be better, again from the liberal persepctive, than any Republican in the current field.
The converse holds for conservative Republicans. Although many Republicans don't seem to realize it, Hillary Clinton should be their choice as the most conservative member of the current Democratic field. Were it not for the widespread conservative perception that Clinton is a pot-smoking, bra-burning, terrorist-coddling pinko, they would embrace her as the least offensive Democrat, even as they hope that, say, Dennis Kucinich gets the Democratic nomination.
Of course, for most voters, it's not especially important to decide which of the opposing party's candidates to root for, but for those who live in open primary states, there is the option of voting in the opposing party's primary and deliberately backing a weak candidate. This is even an option in states with the more conventional closed primary: If you're a Republican, you can switch your registration to Democrat, and then vote for Mike Gravel. Although such spoiler voting occurs, it does not appear to play a major role in American politics.
For pundits, however, strategery is a real possibility. Witness the furor over arch-neocon William Kristol's recent praise for Hillary Clinton. Could Kristol be engaged in a strategic maneuver? Or is this one of those happy circumstances---from the neocon perspective---in which the Democrat that they believe would actually be most sympathetic to their perspective would have serious trouble winning the general precisely because she is erroneously viewed as on the left of her party?