Chief White House economic adviser Lawrence Lindsey Sunday morning said the U.S. economy appears to have bottomed in the second quarter of this year and he expects a solid rebound ahead thanks to the well-timed stimulus of the Bush tax cut. Appearing on NBC television's "Meet the Press," Lindsey said the administration refuses to take the blame for the weaker economy and would make no excuses for the tax cut, even amid Democratic charges that budget raids Social Security funds.