While Prime Minister Stephen Harper is pitching the idea that a Liberal-NDP coalition government would be undemocratic and illegitimate, his senior New Brunswick cabinet minister believes it would be fair play.

The Conservatives have launched an advertising blitz decrying the coalition talks and the opposition cozying up to the Bloc Québécois as a betrayal to the best interests of voters, the economy and the country.

Veterans Affairs Minister Greg Thompson, however, was asked in an interview with CBC News on Tuesday, before Harper's ads began hitting the airwaves, "Do you personally accept the legitimacy of the the Governor General asking the opposition parties to form a coalition [government]?"

He replied, "Well, certainly, because we are in a parliamentary democracy, and at the end of the day, it's a decision for the Governor General to make."

Gov. Gen. Michaëlle Jean was expected back in Ottawa on Wednesday night.

Harper is expected to ask her to prorogue Parliament, giving the Conservatives some breathing room until they can introduce a full budget in January. If she refuses, the opposition parties say they will bring down the government in a confidence motion on Monday.

Harper is planning a 10-minute televised national address on 8 p.m. AT to rally support to prevent the coalition from toppling his government. Liberal Leader Stéphane Dion will respond to the prime minister's address.

Don Desserud, a political science professor at the University of New Brunswick in Saint John, said the Governor General has to be careful not to make the situation worse. If the prime minister requests Parliament be prorogued, Jean will probably have to agree, he said.

"If he asks her for that … she would, in my judgment anyway, be obliged to say yes, for this very reason: what she has to do, in her capacity as Governor General, is to avoid, as long as she possibly can, any sense that she is interfering in the electoral process, in the democratic process, in the parliamentary process … all those things that are the political world," Desserud said.

Desserud said the Governor General doesn't want to be accused of interfering in a partisan way.

David Docherty, a political science professor at Wilfrid Laurier University, said he thinks the prime minister is going to have a difficult time recovering from the fallout of the last few days.

"I think that he will probably wear this defeat personally in the sense that you can't own all the victories and not the big defeat," Docherty said.

"I think it would be very difficult for him to stay on. So I think that he would have to wear this and step down. It could be the end of Mr. Harper's career."