A divided Virginia General Assembly pushed back Wednesday against Gov. Robert F. Mc­Don­nell’s proposed changes to the state budget and other bills — overriding his veto of an effort to raise awards in medical malpractice lawsuits and rejecting his attempt to weaken measures that would require businesses to provide insurance for autistic children and mandate that leak-plagued oil tanks in Fairfax be brought up to code.

But McDonnell (R) scored a major unexpected victory when both chambers voted to allow him to appoint a seat on the Metro Board of Directors, which he had been seeking since his term began.

The governor asked lawmakers who returned to the state Capitol on Wednesday to consider hundreds of amendments to 134 measures in a marathon one-day session.

Lawmakers accepted many of his technical and non-controversial amendments to bills they approved during their legislative session that ended in February, but they rejected his proposed changes to some of the most hot-button issues.

Democrats said McDonnell’s defeats at the hands of even his own party were a sign that he had not adequately taken the legislature’s temperature before delivering a heavy volume of changes. Their comments echoed GOP complaints made in 2007, when Republicans accused then-Gov. Timothy M. Kaine (D) of racking up a sub-par record because the General Assembly rejected two of his vetoes and some of his amendments.

“This type of smackdown of a governor, you don’t see it, except maybe in a governor’s last year,” said Del. Albert Pollard (D-Northumberland).

Republicans said they had informed Mc­Don­nell that some of his spending items were likely to be rejected and described the action as nothing more than the normal push and pull between the branches of government.

“There are some things the executive branch can do,’’ Del. Terry G. Kilgore (R-Scott) said. “And some things where the legislative branch, we want to set our priorities. There’s nothing personal or anything like that.”

In total, Mc­Don­nell amended 133 bills and submitted 86 amendments to the state’s two-year $78 billion budget, which legislators passed unanimously in February — the first time in recent history.

The sheer number of measures the governor tinkered with kept legislators at their desks, hour after hour, considering whether to accept his changes.

“He likes to adjust, amend, tinker,” said Sen. Minority Leader Thomas K. Norment (R-James City County). “So I think it’s very consistent with his legislative personality.”

Legislators overrode McDonnell’s veto of a bill that would raise awards in medical malpractice lawsuits by $50,000 a year starting in 2012.

The Republican-led House voted 93 to 7. The Democratic-controlled Senate voted 29 to 11. The senate briefly delayed its vote after McDonnell lobbied legislators to sustain his veto. “The sign of a good compromise is that there’s something to like about it and there’s something to hate about it for each side,’’ said Del. David B. Albo (R-Fairfax).

Legislators have debated for years whether to increase the awards in such suits. Some Democrats have favored an increase, but Republicans have rejected the plans in the name of tort reform. McDonnell said the bill would not “meaningfully protect against health-care cost increases.” But he told legislators that he vetoed the measure because it violated a campaign promise.

In the 1970s, lawmakers limited awards in medical malpractice suits to $750,000. The amount was gradually increased and reached $2 million in 2008. The bill calls for an increase to $2.05 million starting in 2012, and then $50,000 each year until 2031.

Autism activists cheered legislators’ rejection of a Mc­Don­nell amendment they said would gut a bill designed to require health insurers to pay for a specialized therapy known as applied behavioral analysis, as well as for occupational, speech and other therapies for children ages 2 to 6.

Mc­Don­nell had proposed amendments that were designed to make it less costly for businesses, which consider the proposal a burden they cannot afford in tough economic times.

The bill passed after 11 years of failed attempts.

“When signed, this legislation will be a historic step forward to address early intervention for autism in Virginia,” said Pat DiBari, president of the Virginia Autism Project.

The General Assembly rejected McDonnell’s overhaul of a bill that would require a series of leaky oil tanks in Fairfax to be brought up to code within 10 years. McDonnell wanted to ask the state’s Water Control Board to review its regulations for such sites and to adopt new standards if it deemed it necessary.

Sponsors of the legislation argued that McDonnell’s change would undercut their intention to require upgrades at the facility, which had suffered several recent leaks and was the site of a massive underground plume of oil that damaged homes in the early 1990s. The bill will now return to McDonnell, who will have to decide whether to veto it. Homeowners and local officials in Fairfax are lobbying him to allow the bill to become law.

Mc­Don­nell had worked for months to get a seat on the Metro Board but had been thwarted several times by officials in Northern Virginia, primarily Democrats, who oppose the effort.

The Senate voted 21 to 19 with three Democrats — Northern Virginia Sens. Chap Petersen, Chuck Colgan and Toddy Puller — voting with all Republicans. The House voted 62 to 34.

“Virginia deserves the same representation enjoyed by Maryland and the District of Columbia, and this vote ensures that will be the case,’’ McDonnell spokesman Tucker Martin said. “This is a positive step forward for improving transportation in the Washington, D.C., metro area.’’

The amendment to the state’s two-year $78 billion budget will force the Northern Virginia Transportation Commission, which is composed of 19 local and state elected officials plus the state’s public transportation director, to allow the governor to appoint a member to the board. The NVTC would lose a seat on the panel.

Jay Fisette, NVTC’s chairman, said he was “shocked” that Mc­Don­nell pursued the Metro seat through the state budget, noting that the Washington Metropolitan Area Transit Authority board and the NVTC were already negotiating with him over the issue.

“By doing it in this way, he’s circumvented the process and done an end run around the ongoing conversations,” he said.

The General Assembly rejected a number of McDonnell’s amendments to the state budget. Some died at the hands of House Republicans, including one that would have allowed local governments to require teachers and other employees to begin making a 5 percent annual contribution to their retirement funds. The proposal had been a priority for the governor.

Others fell in the Democratic-led Senate, including an effort by McDonnell to begin phasing out funding for public broadcasting and another for a new optional defined contribution retirement plan for state employees.

The legislature accepted other proposals from the governor, including an addition of nearly $28 million to help shore up the Virginia Retirement System, additional funding for economic development and $2.6 million to improve the Rotunda at the University of Virginia.

In one of the day’s most hotly contested issues, the General Assembly acceded to one of McDonnell’s most controversial changes, an amendment that would restrict insurance coverage for abortion.

He tacked language onto a bill to start a health-care exchange in Virginia — as required by the federal health-care law — that would bar any insurance plan offered as part of the exchange from covering abortion, except in cases of rape, incest or when the life of the mother is at risk.

Abortion opponents have pushed for such language in more than 20 states, arguing that a government-managed health-care market should not include abortion coverage. Abortion rights advocates argue the restriction would bar individuals from spending their own money to buy coverage from companies.

The Senate, where Democrats hold a narrow majority, vigorously debated the restriction but agreed with the GOP-held House to accept the restriction after two Democrats who oppose abortion voted with all 18 of the chamber’s Republicans. The 20-20 tie was broken by Lt. Gov. Bill Bolling (R), an abortion opponent.