Following my blog on Mitt Romney appointing Paul Ryan as his running mate, TIME magazine asked me to write a piece for their international edition. Here it is.

To win a campaign, you have to make the weather. It is one of my golden rules. But whereas the real weather is measurable to the last degree of heat or the last drop of rainfall, the political weather is harder to gauge. Polls can help, but ultimately, it is all about a candidate’s judgment calls.

Right now, Republican presidential challenger Mitt Romney is making the weather with the choice of the young Wisconsin Congressman Paul Ryan as his running mate. Ryan’s back story, including the discovery of his father’s body, working shifts at McDonalds and sticking to a fitness regime that helps him keep his alleged six pack, has quickly entered national and, in political circles at least, global consciousness. His past policy statements and voting records are now being subjected to intense scrutiny, and a picture is emerging of a bright, ambitious, conservative politician positioned somewhat to the right of the man who would be his boss in the White House.

But Republicans ought to have concerns about their new young pin-up, even as Democrats may be worrying that Ryan, 42, has injected much-needed energy into Romney’s thus far rather staid and vague campaign. The weather Romney is now making stems from what seems like a bold decision to pick as running mate someone with hardline views on abortion, guns and government spending. In other words, the things designed to appeal to the Republican base.

Other world leaders follow U.S. presidential elections more closely than any but their own, because the winner becomes an important player in their lives and politics too. So far, Romney’s main impact on London has been to upset the U.K. government with some ill-chosen words on preparations for the London Olympics. Until then, his profile in Europe was relatively low. Policy wonks in Europe saw a Republican trying to move closer to the center, and vie with Obama in a battle of policy moderation. Ryan’s appointment has caused foreign governments to analyze whether a Romney Administration might be more of a change than thus far thought.

The base matters in politics, but it does not follow that you should automatically listen to it. Romney’s predecessor in the battle against Barack Obama, Senator John McCain, listened to his base in choosing Sarah Palin as his running mate. I said at the time that it was “tactically brilliant, strategically disastrous.” Here we come to another golden rule of campaigning—strategy is more important than tactics. Indeed tactics without strategy almost always end in disaster. Palin electrified the base, excited the media, and for a while discomfited the Democrats, much as Ryan is doing now. But McCain’s strategy was rooted in the notion of his own experience and, more  subtly, distancing himself from George W. Bush. His appointment of the unpredictable, right-wing Palin fired a double barreled shotgun through both planks of his then even-keeled campaign.

Ryan is a more substantial figure, with a more thought-through set of policy positions, than Palin. It is nonetheless too early to rule out the possibility that in seeking to excite his base, Romney has alienated voters whose support he needs to win. Here is the most golden of all golden rules for a challenger in a campaign—you cannot succeed without winning the support of at least some who voted for the other side last time round. New Labour’s electoral success in Britain, like Bill Clinton’s in the U.S., was built around the understanding that parties that lose elections have to reach out to voters who rejected them in the past. Does Paul Ryan make it more likely that a disenchanted Obama  voter will vote for Romney? I doubt it.

Ryan has injected genuinely conservative domestic positions into the center of the debate, giving Republicans something to defend and Democrats something to attack. But the minute Romney looks unhappy defending some of those positions—the TV debates will be important on this—you will know that he has confused strategy with tactics, and regrets it. That’s the risk in handing over weather-making duties to a running mate. 

We have plenty of time to find out whether Romney’s appointment of Ryan ultimately helps him or Obama most. U.S. presidential campaigns are the toughest of them all, and as Clinton once told me, in a conversation I recorded in my diary at the time, election campaigns are the one form of activity designed to make us all look like our passport photo.

— Campbell was Tony Blair’s spokesman and strategist for Blair’s three U.K. election wins. He recently published the fourth volume of his diaries, Burden of Power