The top-performing market-timing newsletter of the past three decades has turned “aggressively bullish”, Mark Hulbert writes on MarketWatch.com.

The Chartist, edited by Dan Sullivan, has the best track record of any of the market-timing letters Hulbert has followed since his Hulbert Financial Digest began tracking newsletter performance nearly 30 years ago. “In a communication to subscribers Monday evening, Sullivan recommended that subscribers move from being only partially invested in equities to being fully invested,” Hulbert writes. “And in his most aggressive model portfolio, he actually moved to being 125% invested — in other words, to be 25% on margin.”

Hulbert says that Sullivan didn’t lay out his rationale for the increase in his bullishness. But he notes that in his most recent newsletter, dated May 21, Sullivan had this to say: “During the early stages of bull markets, many investors will remain on the sidelines. They have a preconceived idea of where the market will go and will cite any number of economic concerns, as well as the warnings of CNBC pundits, to support their bearish case. Don’t get us wrong; they might be right, but if history is any guide, the great majority of investors who were badly mauled during the bear market will not commit even a portion of their capital until it is much too late.”

Hulbert also notes that Sullivan has made several “prescient” market calls over the years, including his sell signal in mid-January 2008. When he started buying again in April, the Dow had lost a third of its value.