After warning anew of a possible slowdown, President-elect Bush is taking stock of the economy in a gathering of business leaders from throughout the nation, many of whom have bought stock, of a sort, in his selection. Nearly three dozen executives from new and old economy ventures are to gather behind closed doors today with Bush, who’s seeking to build support for his $1.3 trillion 10-year tax cut proposal. Almost two-thirds of the corporate executives planning to attend the economic forum contributed to Bush’s campaign for the White House. Of the 32 attending the event at the Texas Governor’s Mansion, 21 gave to Bush — all but one the legal maximum $1,000 to a campaign that raised a record $100 million. In addition, the attendees’ companies contributed more than $7 million to Republican Party committees, some of which went for so-called “issue ads” supporting the Bush candidacy.