What was intended to be a showcase for Sen Howard Baker's presidential candidacy in Maryland and a windfall for the state's Republican Party turned into a humiliation for both yesterday as Baker abruptly retracted a commitment to speak at a party dinner next week, explaining that he would rather go to Maine.

Maryland's Republican Party chairman, Allen C. Levey, who was expecting more the 600 Republicans to drop $25 each into the party coffers for the Jan. 25 event, called it "an insult and an outrage."

In return, Baker's campaign chairman, Wyatt Stewart, called Levey's remarks "unfair and politically unconscionable."

And state Sen. Howard Denis (R-Montgomery), who as Baker's state campaign chairman was charged yesterday with the unhappy task of mollifying state Republicans, said miserably, "One of the things they say about Baker is that he has the inability to make hard decisions. Well, here's a hard decision for you -- right in the face."

Baker has been scheduled to appear at one of the state party's "presidential dinners" at the Sheraton Lanham hotel in Prince George's County. Both Ronald Reagan and John Connally have already appeared for similar events, which are designed to give the presidential candidates a chance for exposure before state leaders while rejuvenating the party's nearly empty treasury.

According to Levey, more than 400 tickets had already been sold for the Baker event, and "there were many more to come." Prince George's County Executive Lawrence Hogan had just picked up 100 tickets to sell, Levey said, and U.S. Sen. Charles Mathias had promised both to sell tickets and to introduce Baker at the dinner.

Then, with no warning, Baker aides called state party officials yesterday morning to say that their candidate has decided to attend a dinner for Republican Party leaders in Portland, Maine, where presidential caucuses begin next month.

"I was told that this is a political decision and I have to understand this," said Levey, who immediately canceled the Maryland event. "But it makes me wonder whether Baker can be counted on to keep his commitments. And even if his strategy works, I question whether there will be a great deal of people in Maryland who will want to support him."

That blast set off Stewart, who angrily replied that he had offered to send both Baker's daughter and his campaign chairman, Sen. Richard Lugar (R-Indiana), to appear at the dinner, that Baker could raise more money in Maryland than anyone believed, and that Levey was probably a Connally supporter anyway.

"We made a difficult political decision and I don't think Levey needed to cancel the dinner or treat us this way," Stewart said. "We could raise more money for the Maryland Republican Party than Allen Levey ever dreamed if he would just be reasonable and cool off."

Meanwhile, back in Maryland, Denis spent the day attempting to repair the bridge his candidate had burned. "There's some very unhappy people in various stages of hysteria," he said late in the afternoon. "To put it mildly."

"But our main objective nationally," Denis added, "is to survive. If Baker can do well in Maine and Iowa and stay in the race, people will forget about this, or at least think about it and understand. He's a candidate who's tailormade for Maryland Republicans."

The only state Republican not upset yesterday seemed to be Hogan, who recalled that he had missed many a political dinner in his time. "I'm not mad," said the traditionally feisty Prince George's executive. "I'm sure Baker has got a good reason, because politicians don't like to make anybody mad without a good reason."