Republicans appear to have outmaneuvered Gov. Terry McAuliffe in a state budget standoff by persuading a Democratic senator to resign his seat, at least temporarily giving the GOP control of the chamber and possibly dooming the governor’s push to expand Medicaid under the Affordable Care Act.

Sen. Phillip P. Puckett (D-Russell) will announce his resignation Monday, effective immediately, paving the way to appoint his daughter to a judgeship and Puckett to the job of deputy director of the state tobacco commission, three people familiar with the plan said Sunday. They spoke on the condition of anonymity because they were not authorized to discuss the matter.

The news prompted outrage among Democrats — and accusations that Republicans were trying to buy the Senate with job offers in order to thwart McAuliffe’s proposal to expand health coverage to 400,000 low-income Virginians.

Del. Scott A. Surovell (D-Fairfax) said Republicans were unable to win the policy argument about Medicaid expansion, so they have resorted to other means.

“It’s astounding to me. The House Republican caucus will do anything and everything to prevent low-income Virginians from getting health care. . . . They figure the only way they could win was to give a job to a state senator,” Surovell said. “At least they can’t offer Terry McAuliffe a job. I hope Terry continues to stand up to these bullies.”

Puckett, a senator since 1998, did not respond to calls seeking comment. Other Republicans denied that Puckett was offered the jobs in exchange for his resignation.

In a statement, McAuliffe (D) acknowledged that Puckett’s resignation had created “uncertainty” for his plan to expand the federal-state health program for the poor to 400,000 uninsured Virginians. But he contended that he still had a majority of the Senate on his side.

“I am deeply disappointed by this news and the uncertainty it creates at a time when 400,000 Virginians are waiting for access to quality health care, especially those in Southwest Virginia,” McAuliffe said. “This situation is unacceptable, but the bipartisan majority in the Senate and I will continue to work hard to put Virginians first and find compromise on a budget that closes the coverage gap.”

Senate Republicans, meanwhile, issued a statement praising Puckett. “Although Senator Puckett has decided to end his tenure in the Senate of Virginia, his legacy there will endure,” said Senate Minority Leader Thomas K. Norment Jr. (James City). “And, his commitment and service to the people of Southwest, who honored him with their votes in five successive elections, will continue.”

Senate Majority Leader Richard L. Saslaw (D-Fairfax) confirmed in a brief telephone interview that Puckett would resign Monday. Del. Terry G. Kilgore (R-Scott), chairman of the commission, confirmed that its executive committee is expected to meet and consider appointing him, perhaps this week.

Kilgore disputed the notion that Puckett was resigning in exchange for the tobacco commission job, but he said the resignation made Puckett available to take the position, which involves awarding economic development grants funded by the national tobacco litigation settlement. Puckett’s salary would be determined by the commission, Kilgore said.

“If he’s available, we would like to have him because of his knowledge of the area, and he formerly was on the tobacco commission for years, and he knew what we’re about,” Kilgore said.

Puckett’s unexpected departure will give the GOP a 20-to-19 majority in the Senate at a time when McAuliffe was counting on Senate support for his Medicaid plan. The GOP-dominated House is firmly opposed, and the disagreement has led to a budget standoff that could trigger a government shutdown if it is not resolved before the start of the new fiscal year, July 1. In addition, Puckett’s district is heavily Republican, and it will be difficult for Democrats to retain the seat in a special election and hang on to control of the Senate overall.

Puckett’s exit does not immediately sink McAuliffe’s chances in the Senate because three moderate Republicans in that chamber support expansion. But some of McAuliffe’s Senate allies have recently signaled their discomfort with the idea of letting the Medicaid push trigger a government shutdown.

And the resignation will come as two prominent Democrats are out of Virginia. Saslaw is in California visiting his newborn grandchild. Sen. Janet D. Howell (D-Fairfax) is leaving on Thursday on a trip to South Africa that is expected to last through June 24. But she said she will return earlier if she is needed.

Once Puckett resigns, Senate Republicans are expected to take advantage of their newfound majority by calling members back to Richmond — something that nine members of the Senate can make happen. The legislature has been in a special session for months but has not been meeting regularly. With the Senate back in Richmond, the chamber’s new Republican majority could pass a budget without Medicaid expansion.

Less clear is whether Democrats, including McAuliffe, have any recourse to block the job appointments that Puckett apparently negotiated. Although the executive director of the Tobacco Indemnification and Community Revitalization Commission is a gubernatorial appointee, it is the commission, not the governor, that controls job appointments below that level. The commission is a 31-member body made up of legislative and gubernatorial appointees; its chairman and vice chairman are Republicans.

Judicial appointments at the level of district judge are strictly a legislative prerogative in Virginia.

Puckett’s daughter, Martha Puckett Ketron, is already on the bench in Southwest Virginia, serving as a Juvenile and Domestic Relations District Court judge. Circuit Court judges in that region gave her a temporary appointment last year while the General Assembly was not in session. The House approved her appointment to a six-year term when it reconvened early this year, but the Senate declined to confirm her. The Senate has a policy against appointing the relatives of active legislators to the bench.

After the legislature concluded its regular session in February, the judges reappointed Ketron to serve until the legislature reconvenes. If Puckett resigns, the legislature plans to appoint her to a full six-year term. “It should pave the way for his daughter,” Kilgore said of Puckett’s resignation. “She’s a good judge. . . . I would say that he wanted to make sure his daughter kept her judgeship. A father’s going do that.”

During the General Assembly session this year, Republicans cried foul when McAuliffe appointed longtime GOP operative Boyd Marcus, who had crossed party lines to endorse McAuliffe in the campaign, to a six-figure position on the Virginia Alcoholic Beverage Control Board. Republicans blocked the appointment, saying the job was essentially “sold” for the endorsement.

Michael Laris contributed to this report.