Gov. Harry Hughes' plan to rescue Maryland's troubled horseracing industry, after being dissolved and redrafted by legislators five times in the last three days, has come galloping out of a House committee only to be almost destroyed by the Senate Finance Committee.

Two very different bills are now approaching the floors of the two houses, with less than two weeks to go in the session to iron out the differences. Both contain the new feature of a state racing authority, which would have power to negotiate a contract to buy out and temporarily operate the Bowie racetrack.

Hughes has endorsed the House version of the bill, which empowers the authority to buy Bowie for up to $12 million. He has not yet commented on the Senate version, which would not allow the authority to buy Bowie unless the legislature votes -- presumably in 1982 -- on the proposed contract.

Both bills provide for the eventual closing of Bowie, leaving two one-mile thoroughbred horseracing tracks in Maryland -- Laurel and Pimlico. The two remaining tracks would be allowed to lease Bowie's 96 racing days after the Bowie track was closed. This consolidation of racing at two tracks is believed by its supporters to offer a solution to the tracks' chronic financial problems.

The radical, last-minute surgery on Hughes' original bill has prompted some legislators to warn that the tarnished political history of horseracing may be about to repeat itself. And racetrack lobbyists were complaining that they don't know whether to support or fight the proposal, because, according to one, "It changes every 15 minutes."

Hughes originally proposed that the state buy Bowie's franchise for $6 million, while leaving its owners with the 476 acres on which the track is located. The 96-day racing season would then be divided between Laurel and Pimlico.

That proposal appeared doomed because legislators were loathe to spend $6 million for something intangible. The new proposal to spend $12 million for the track and the 96-day racing season is being touted as more politically palatable since the state would acquire real property and would then own a going concern.

This measure passed the House Ways and Means Committee at midnight last night. Six of 16 committee members voted against it, complaining that the $12 million price tag was too high. Supporters insisted mhat Bowie's owners would not take anything less than $12 million, and that the price was a reasonable one if the plan succeeded in rescuing the $600 million-a-year industry.

The Senate Finance Committee today refused to pass such a broad measure and instead empowered the authority only to negotiate a selling price -- not to buy out the track -- until the legislature can review it.

Meanwhile, a one-cent-per-gallon gasoline tax increase sought by Senate leaders and recently endorsed by Hughes easily passed a preliminary test on the Senate floor tonight, indicating strong support for the measure.

The Senate voted 32 to 11 to adopt compromise amendments intended to pacify rural senators. As amended, the bill would increase the state's 9-cent-per-gallon tax by one cent a gallon every year beginning next July 1 and ending after five years.

Hughes has tied the tax increase, which would raise $20 million next year, to a plan to transfer revenues from the state transportation fund to general budget accounts, easing the state's fiscal squeeze and allowing for a $500 across-the-board raise for state employes.

But Senate leaders made it clear that they believe any money raised through increased transportation taxes should be left in the transportation fund to pay for road and bridge projects.

In other action today:

The Senate gave preliminary approval to a measure giving limited protection to tenants of buildings being converted to condominiums. The bill is a top legislative priority of Montgomery County Executive Charles W. Gilchrist, whose county has recently experienced a rash of apartment building conversions.

Two measures toughening Maryland's drunk driving laws emerged from the House Judiciary Committee as part of the governor's package of bills dealing with alcohol-related traffic offenses.

The most controversial measure would lower the permissible levels of blood alcohol content from the current .15 to .13 for driving while intoxicated, and from the current .10 to .08 for driving while impaired.

The committee also approved a Senate-passed bill that would close a loophole: the measure would bar persons whose licenses have been suspended or revoked from driving to and from work.

The House Appropriations Committee sent to a summer study session two bills that would give state employes the right to bargain collectively. A Senate committee has already taken the same action, killing the issue for this session.