WASHINGTON _ President Barack Obama faces a barrage of questions on his plans to reinvigorate the economy with a massive stimulus bill and additional mark_on-billion-mark_off’s in bailout money for the financial markets. Trips Monday and Tuesday to cities hurting under the economic meltdown and a prime-time news conference Monday night show that Obama and his advisers are worried about a looming Senate vote on the stimulus bill, which failed to gather meaningful Republican support during rare weekend debate