Major stock market indexes are trading near all-time highs, but could start to decline ahead of a looming government shutdown that could occur as early as next week.Government Shutdown LoomsWednesday, Oct. 1, marks the deadline for a potential government shutdown if Congress does not reach an agreement on a funding bill or a temporary extension.Democrats are pushing for an extension to healthcare benefits under the Affordable Care Act, while Republican members appear unwilling to negotiate on the matter.Sen ...