Mr. Outside-turned-Mr. Inside has gone outside again.

Eighteen months after Rep. Newt Gingrich shed his mantle as the street fighter of the Republican right by winning election as minority whip, his party's No. 2 leadership post in the House, the Georgia Republican has taken up arms again. This time, he is fighting not just his usual foes in the Democratic leadership but his own president and a considerable part of his own party in trying to torpedo the $500 billion deficit-reduction package that President Bush has embraced.

To many Democrats, Gingrich has merely reverted to form, once again adopting the kind of slashing attack style he used in the ethics fight that led to the resignation last year of Speaker Jim Wright (D-Tex.). By throwing sand in the gears of government, Democrats charge, Gingrich thinks he can prove to American voters that Congress is so inept and venal that only Republicans led by him can save it.

"His sole goal in life is to control the House," said Rep. Dennis E. Eckart (D-Ohio). "To control the House he has to destroy it."

"He's so institutionalized in the minority, he really doesn't know how to govern," said Rep. Vic Fazio (D-Calif.). "He wants Democrats in Congress to not look capable of governing."

But to Gingrich and his allies, the decision to oppose Bush and other Republican leaders on the budget agreement is a case of maintaining allegiance to a broader movement that the Georgia Republican calls "reform populist conservatism" that they believe will lead to Republican control of Congress.

"Real leadership is not risk-free," Gingrich said yesterday.

In publicly breaking with the president and the top Republican leader in the House, Rep. Robert H. Michel (R-Ill.), Gingrich has climbed back out on the high wire where he has spent much of his political career. The tightrope act could provoke a rebellion by Republican colleagues who believe that his disloyalty disqualifies him from being a party leader. But Gingrich and his cadre of followers see it as a calculated gamble in their long-term quest to gain Republican control of the House and to wrest the leadership of the House GOP from what they view as the party's accommodationist wing.

As he has done during most of his political life, Gingrich is addressing a constituency beyond Capitol Hill, where he believes a populist opposition to a budget plan loaded with painful spending cuts and tax increases will find a receptive audience and enhance the appeal of the GOP's right wing to middle class voters. He and his supporters expect to lose this fight, but they consider it only a skirmish in a a long-term war.

The prospect frightens Democrats, who see Gingrich's description of the deal as unfair to ordinary voters as a direct appeal to Democratic constituencies.

"The long-term gamble here is enormous," said Rep. Marty Russo (D-Ill.). "It's all our people who are being taxed and cut, and our handprints are all over it."

After spending months as a member of the Republican negotiating team in the budget summit, Gingrich emerged from a House GOP caucus Monday and blistered the deficit reduction agreement as an anti-growth prescription for recession. His opposition took on added importance because congressional Democrats are demanding that a majority of Republicans in both the House and the Senate vote for the budget agreement as the price of Democratic support.

In breaking with the White House, Gingrich laid bare the inherent tensions between a style of politics he has brandished since his election to the House in 1978 and the responsibilities as a party leader he assumed when he won election as minority whip by just two votes in March 1989.

He also infuriated some of the moderate Republicans to whom he owed his election, a group that at the time was convinced that bringing Gingrich into the leadership would both give the House GOP a more assertive posture and temper the Georgia Republican's go-for-the-throat style.

"I think a person has to decide whether he has to lead or have his own agenda," said Rep. Rod Chandler, a moderate Washington Republican who supported Gingrich for party whip. "It may be Newt has chosen his own agenda, and if that's the case I am going to look for a new leader. I voted for a guy who promised to bring the party together. If you can't be there {for the president}, then as a leader you either resign or keep your mouth shut."

But Gingrich is neither the resigning type nor one to keep his mouth shut.

"I'm not on the president's staff," Gingrich said with trademark bravado. His allegiance, he said, is first to his suburban Atlanta district and second to the conservative movement.

Some Democrats see Gingrich's opposition to the budget deal as a warm-up for a coup attempt against Michel before the 102nd Congress convenes next year. "It's the opening shot at trying to run against Bob Michel," said former representative Tony Coelho (D-Calif.), who knows Gingrich well.

But Rep. Vin Weber (R-Minn.), a Gingrich ally, said Gingrich is "an ambitious guy but he's not dumb enough to pick a fight with the president to advance his own interests."

The real objective, said Weber, is to position the conservative wing of the House GOP behind pro-growth economic policies in order to avoid blame for a recession if it comes and to prosper in 1992, when redistricting is expected to provide Republicans with their best chance in decades to gain control of the House.

"It's always complicated to be at odds with your president, but long term it may well be the right position for him to be in," said Weber. Republican House members and Republican congressional challengers, he added, will thrive and cut into the Democratic electoral base "by being on the right side of economic issues."

"It's a roll of the dice," said Coelho, "but it's not unusual for Newt."