(Reuters) - U.S. Senate Republicans were expected to vote on Tuesday for opening debate on a healthcare bill without knowing what is in it, but the potential components of the legislation were clear.  Approaches hammered out by Republicans in recent months were expected to be in the mix, with Senate Majority Leader Mitch McConnell making key choices about what is in and what is out, based on how much support a given combination can attract. One bill he could introduce would repeal much of Obamacare with no replacement plan. Another bill could repeal and replace the 2010 law while also overhauling Medicaid, the federal health insurance program for the poor and disabled. Both bills have faced criticism from the health industry.  The Affordable Care Act, dubbed Obamacare, extended insurance to 20 million Americans and was Democratic former President Barack Obama’s signature domestic achievement. For seven years, Republicans have promised to repeal and replace it, but have struggled to do so, even though they now control both chambers of Congress and the White House. Another path open to McConnell would be to develop an entirely new bill on the Senate floor through amendments. Here are summaries of bills that could be in play: A shortened version of Obamacare repeal, called a “skinny repeal,” could end Obamacare’s individual and employer mandates and the medical device tax, said a Senate aide and a lobbyist. Senate Republicans would likely go for a bare-minimum “skinny repeal” only if other approaches, such as those below, cannot win approval. McConnell has said he could introduce a bill that Republicans passed in 2015 that was subsequently vetoed by Obama, called the Obamacare Repeal Reconciliation Act. It would repeal most Obamacare taxes and end funding for Obamacare’s Medicaid expansion, as well as tax credits that help low-income people buy health insurance on the individual insurance market. It would abolish a penalty on individuals who do not purchase insurance, as well as a penalty on certain employers who do not provide employees insurance. But the legislation does not include a replacement plan. If signed into law, Congress would have two years to craft and pass a replacement. The nonpartisan Congressional Budget Office (CBO) estimated the law would increase the number of uninsured Americans by 17 million in 2018, and by 32 million in 2026. The Senate has spent months negotiating a bill, called the Better Care Reconciliation Act, that would repeal and replace much of Obamacare, while also drastically cutting Medicaid. The latest version would repeal many Obamacare taxes, but retain two taxes on the wealthy. It would unwind Obamacare’s Medicaid expansion over three years, then slash spending on Medicaid beginning in 2025, as well as overhaul the law’s tax credits. It would also eliminate penalties on individuals for not purchasing insurance and employers who do not provide it. The bill includes an amendment from Senator Ted Cruz that would let insurers sell bare-bones policies that fall short of broad benefits mandated under Obamacare, such as maternity and newborn care and prescription drugs. The CBO estimated the bill would result in 22 million more people losing their insurance by 2026 and, in a separate report, estimated that Medicaid would be cut by 35 percent come 2036.  HOUSE-PASSED LEGISLATION In May, the House of Representatives passed its own version of healthcare legislation, called the American Health Care Act.  It would repeal most Obamacare taxes, including taxes on the wealthy, replace the law’s income-based tax credits with flat age-based credits capped at upper-income levels and end funding for the Medicaid expansion beginning in 2020.  Like the Senate legislation, it would eliminate the penalty on individuals who do not purchase insurance and employers who do not provide it to employees. Controversially, the House bill would eliminate the Obamacare mandate that insurers charge sick and healthy people the same rates. The CBO found it would result in 23 million more uninsured Americans by 2026 and destabilize the individual insurance market in much of the country. 
Factbox: What might be in Senate's mystery healthcare bill