Smaller-than-expected tax refunds and rising individual tax receipts will pare back federal borrowing significantly for the first half of this year and could reduce the $521 billion deficit projected for the fiscal year by as much as $100 billion, Treasury and congressional budget officials said yesterday. The Treasury Department's borrowing estimates may prove to be more good news for President Bush on the economic front, as opponents attempt to make his fiscal stewardship a campaign issue. The $184 billion the government is now expected to borrow through June is a 27 percent improvement from Treasury's February projection of $252 billion,...