Unencumbered by arithmetic or concern for the welfare of Floridians without health insurance, lawmakers in Tallahassee are rushing headlong to reject the proposed Medicaid expansion that would cover some 900,000 state residents who don’t have healthcare protection today.

In an astonishing rebuff to Gov. Rick Scott, a Senate panel joined its House counterpart this week in turning thumbs down on the federal government’s offer to pay 100 percent of the expansion for three years. This indefensible disregard for Florida’s most vulnerable ignores the advice of healthcare professionals, the business community and the needs of taxpayer-supported public hospitals, who have to treat everyone who walks in.

Never mind that the state’s own economists projected just last week that endorsing the expansion would reap a bonanza of $51 billion over 10 years, in return for an expenditure of $5.2 billion.

Never mind that Gov. Scott, a hard-line conservative Republican who once opposed all aspects of the Affordable Care Act, finally acknowledged last month that it makes no sense to deny expanded Medicaid to Floridians while other Americans get the benefit of this tax-supported program.

Never mind that a host of studies show expanded Medicaid would create jobs. An economist for Moody’s said it would create 10,000 to 30,000 jobs in the state over 10 years. Another study done for the Florida Hospital Association (FHA) estimated that it would add 56,000 jobs.

Never mind that pro-consumer healthcare organizations have endorsed the move because it will improve the healthcare of Floridians. Even the Florida Chamber of Commerce gave conditional approval to the expansion, providing the Legislature monitors it closely to keep a lid on costs and limits the impact on private insurers.

Never mind that a state poll by the FHA found that 62 percent of Floridians approve the expansion.

Never mind that the federal government accommodated Florida’s request for a waiver so that Florida could bring its Medicaid progam under managed care (HMOs) because the state believes this will save money.

And never mind that expanded Medicaid promotes the mission of public hospitals to provide medical care for all. Jackson Hospital in Miami-Dade estimates that the expansion would cover a substantial portion of the 7,800 annual admissions of patients without insurance.

In spite of these many reasons and others to endorse Medicaid expansion, Florida’s Republican-controlled Legislature prefers to play politics with the issue, mindful that Gov. Scott was labeled a turncoat by tea party activists after he embraced the expansion.

One thing they seem to get: Just saying No to the federal government’s generous offer would be irresponsible, so they are searching for a better alternative. Why?

The expansion with rules specifically tailored for Florida already has federal approval — it’s a sure thing. Alternative plans being floated by Arkansas and other states aren’t. They haven’t been finalized and they could cost more.

Gov. Scott says he supports expansion but seems unprepared to push legislators to reach that goal. The governor should steal a page from another rock-ribbed conservative, Arizona Gov. Jan Brewer, who after first dismissing “Obamacare” has now come out in full support of Medicaid expansion because it’s a win for her state.

It would be indefensible for Gov. Scott to back away from this fight. It’s not only morally right — it makes good business sense for Florida taxpayers.