The Democrats yesterday looked over what the Republicans had wrought in Detroit and some of what they saw pleased them.

They especially liked the contortions that Ronald Reagan went through in selecting a running mate and hoped that what Democratic Party Chairman John White called "Wednesday night's fiasco" was just a preview of the ability of Reagan and his organization to deal with the pressures of a general election campaign.

They also liked the end product of the vice presidential selection process, George Bush, because he was so obviously Reagan's second choice and because there are differences between Bush and Reagan that the Democrats believe can be exploited.

And they liked that part of Reagan's Thursday night acceptance speech when he promised "an immediate and thorough freeze on federal hiring" -- they liked it so much that yesterday the administration rolled out some of its management heavyweights to announce that there already is such a freeze, imposed by President Carter.

For the opposition party, these were the highlights of the Republican National Convention, which in the view of White and other Carter supporters could have and should have been better for the Republicans -- and therefore worse for the Democrats.

But there is no getting around the fact that the Republicans left Detroit a unified party, that they ran a far smoother convention than the Democrats can hope to next month in New York, and that Reagan once again proved himself a smooth and effective political performer on television.

At the White House and the Carter reelection committee yesterday, aides to the president repeatedly called Reagan a formidable opponent and vowed not to repeat the mistake of others by underestimating the ability and attraction of the movie star-turned-politician.

Their assessment of Reagan's acceptance speech ran from the grudging comment of a White House official that it was "a slick performance" to White's statement that Reagan is "as good a performer as I have ever seen."

Still, the prevailing view among Carter supporters yesterday was that, given the president's political problems, the divisions in the Democratic Party and the control the Reagan forces exercised in Detroit, the Republicans failed to make the most of their four-day nationally televised convention.

In its aftermath, the beginnings of the Carter strategy for confronting Reagan began to emerge.

It will be to portray the former California governor as a man who neither understands nor cares about the presidency and who springs from the narrowest of political bases, with little in common with the vast majority of Americans. o

In this, the Carter aides believe Reagan handed them a gift Wednesday night with his brief and embarrassingly public flirtation with former president Gerald Ford for the second spot on the ticket and the negotiations over just what powers Reagan, as president, would be willing to surrender to Ford.

While there was disagreement over whether the episode will cause Reagan any permanent political damage, it clearly played into the White House's hands in trying to portray Reagan as simply not up to dealing with the burdens and pressures of the presidency.

"The bottom line is that it was his first major decision in pursuit of the presidency and he blew it," said Richard Moe, Vice President Mondale's chief of staff.

"He had two months to consider this and establish a selection process, but he crammed it all into 30 frantic hours in Detroit. To seriously consider sharing the powers of the presidency demonstrates Reagan's lack of comprehension of what this office is all about."

Reagan's turn to Bush as a running mate was mildly pleasing to the Democrats because Bush was his second choice.

"Reagan is not coming out of that convention as strong as I thought he would," one White House official said. "Bush is clearly the second choice. The gloss is off. There are a lot of issues to reconcile between them."

While Bush now embraces the Republican platform, there are aspects of it -- its absence of support for the Equal Rights Amendment, for example -- that he opposes.

The White House will not let Bush forget that as it seeks to bind the two Republican nominees to the principles of what White called a "hard-line, harsh, right-wing" document.

The process of trying to paint Reagan and Bush into a corner on the far right side of the room began even before the GOP nominee had delivered his acceptance speech.

At a Democratic Party fund-raiser in Hollywood, Fla., Thursday night, the president portrayed the Republicans as narrow-minded and fearful, and rattled off a litany of past GOP sins that included opposition to the minimum wage and rural free delivery of mail.

Yesterday, Carter's campaign chairman, Robert S. Strauss, picked up on that theme. He said the Republicans had "looked good" in Detroit in constructing a "hard, conservative platform."

"Then their nominee made a speech that bore no relationship to their platform or the convention to that day," Strauss said. "In essence, the Republicans spent three days appealing to the delegates in the hall and on the fourth night tried to forget it all and appeal to a broader segment of the American public. I don't know if that connection was made."

The Democrats will convene in New York in about three weeks for, in Strauss' words, a "different" sort of affair than the one the Republicans staged in Detroit. For one thing, there will be no way to conceal the divisions in the party and between supporters of Carter and Sen. Edward M. Kennedy (D-Mass.).

According to White, there are already so many minority reports on the platform and rules on file with convention officials that if all were fully debated, the Democrats would be in session for 60 hours, a "disaster" the party chairman is working to avert.

But those divisions, if they do not get out of hand, could be an asset when contrasted with the lack of political debate that marked the Republican convention, White said.

"The Republicans' basic weakness is the narrow approach they took, but they will have to live with it," he said.

"It will be good for us to show a little difference of opinion. They have a narrow view of America. I hope we present a broader picture."