One of the linchpins of the federal health care law passed last year is a requirement that each state establish an insurance exchange ? a marketplace where individuals and small businesses can compare and buy private insurance plans. The federal government will provide states with startup money to establish exchanges, which must be open for business by 2014. If a state declines to start one, the federal government can step in and do it. With a January 2013 deadline to have an exchange plan ready, lawmakers in Missouri —particularly conservatives who have been outspoken in opposing the healthcare law—face a difficult proposition: set up the healthcare plan many of them oppose or do nothing and invite even more federal intervention.