There is still a year and a half before the next U.S. presidential election, but campaigning is already intense. Even though there is no shortage of candidates from the two main parties, attention is now focusing on an as-yet undeclared candidate who may run as an independent. His denials notwithstanding, the decision of New York City Mayor Michael Bloomberg to leave the Republican Party looks a lot like the first step in a bid for the top job in the United States.

Mr. Bloomberg is a billionaire businessman who made his money — estimated at more than $5 billion — by establishing the financial news service that bears his name. Despite being a life-long Democrat, he joined the Republican Party in 2001 to win its nomination for mayor of New York City, a race he won and a job for which he was re-elected in 2005. Barred from seeking a third term, he must focus on other horizons.

Mr. Bloomberg has consistently said that he does not want to run for president, but by all appearances his team has been laying the groundwork for such a bid for several years. In recent months, he has been traveling the U.S. extensively and sharply critiquing the current administration for squandering U.S. leadership, and national politics generally for bitter partisanship and a refusal to tackle tough and pressing national issues. Mr. Bloomberg is positioning himself as a centrist, straight-talking politician who is focused on results, not rhetoric or ideology. On a recent trip to California, he used that theme to win over audiences — while appearing with that state's maverick governor, Mr. Arnold Schwarzenegger. He will soon visit other key states to see how his message is received.