WASHINGTON (AP) -- Congress is racing to close out a $1.1 trillion spending bill by Dec. 11 and avoid a holiday season government shutdown.
At issue are dozens of policy provisions attached to the 12 spending bills. When a bill has trouble advancing on its own, lawmakers often try to add it to the spending legislation.
For powerful interest groups such as banks, broadcasters and agribusiness, these so-called riders are often the last, best chance to push items on their agenda through Congress.
Republicans have attached provisions that take on Obama's health overhaul, new environmental regulations and the 2010 Dodd-Frank law tightening oversight of the financial services industry.
If history is any guide, Obama and Democrats -- whose votes will be needed to pass the catch-all spending bill -- will avoid most of them.
But lots of lower-tier issues are in play.
Anti-Castro forces in the House of representatives appear unlikely to reverse Obama's moves to loosen rules about traveling to Cuba. But supporters of medical marijuana are hopeful they can win new guarantees against harassment by federal authorities.
Some conservatives are still pressing to use the spending legislation as a way to take away federal money for Planned Parenthood, a national organization that offers women's health services that include abortions. They also want to increase scrutiny of Syrian and Iraqi refugees seeking to settle in the U.S.
What to know about riders and how they make it into legislation, or don't:
VETO THREATS MATTER
Presidents invariably do well in negotiations on riders, and veto threats can force the removal of the most contentious policy add-ons.
Obama is issuing veto threats as freely as ever. This time, it means Republican attempts probably won't make the cut on blocking rules on power plant emissions, delaying ozone standards and weakening clean water standards involving mountaintop removal coal-mining operations.
Any rider with bipartisan support has a greater chance of making it.
The financial services industry can claim some Democratic support for exemptions to some new regulatory burdens. Watchdogs such as Sen. Elizabeth Warren warn against efforts to "weaken, delay or dilute the rules that protect consumers and hold big banks accountable." Warren was on the losing end last year over easing restrictions on banks that wanted to trade in risky financial items known as derivatives.
IF IT'S HAPPENED BEFORE, IT'LL HAPPEN AGAIN
Once a rider is added the first time, the battle usually is over.
Some repeat provisions would block the Environmental Protection Agency from regulating the lead content of ammunition; ban federal dollars for needle exchange programs for addicts threatened by HIV; renew several long-standing provisions on abortion; and block the Justice Department from interfering with medical marijuana dispensaries.