He is there every day, usually wearing a conservative blue suit that matches his ideology-a watchdog at the gates, trying to prevent Democratic proposals from becoming the law of the land.

Rep. Robert E. Bauman (R-Md.) is simply doing what comes naturally: manning the battlements of the House floor and staging guerrilla warfare on the Democratic majority.

He relishes delaying tactics. He has an endless supply of points of order and parliamentary maneuvers to harass the opposition. He insists upon "putting the House on record," as Bauman calls it, by demanding recorded votes.

Until this Congress, Democrats brushed him off as bothersome and pesky but not significant enough to cause them to change their ways. "Every legislature needs a Bauman," House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) once said, as if to say every picnic needs a fly.

Now that assessment is changing. Bauman is winning some votes. He is branching out, taking an interest in more substantive issues.

He successfully led the move to cut foreign aid to Panama, a step that tipped off the Democratic leadership to the deep trouble facing legislation to implement the Panama Canal treaties.

He is considering a race for the seat of liberal Republican Sen. Charles McC-Mathias (Md.) in 1980. And he has just become chairman of the 250,000-member American Conservative Union, which gives him a forum for becoming better known nationally along with a fund-raising and grass-roots lobbying base.

Bauman used his position on the Merchant Marine Committee to alter the Panama Canal enabling legislation to the point that the administration is saying it comes close to violating the treaties. He has become the point man in the issue of lifting economic sanctions against Rhodesia, an issue he has a good chance of winning. And he has been appointed to the Rules Committee, through which most legislation must pass to reach the floor.

The change in Bauman's fortune is mostly symbolic of the times. Ideas once considered narrowly conservative are now getting serious attention as the House responds to the mood of the country. Bauman admits, "Conservatives can't take credit for that. The times are with us."

"In the old days, if we got an amendment cleared with the chairman and ranking Republican we were home free," said an aide to a major House committee. "Now we have to clear it with Bauman."

A Democratic vote-counter told Bauman:

"It used to be we could tell Democrats coming on to the floor for a vote it was a Bauman amendment and we would get an automatic "no" vote. Now they want to know what the amendment's about."

Bauman went to Congress in 1973 special election to fill the Eastern Shore seat.

With only a short interruption, he has worked on Capitol Hill since he was a Capitol page at the age of 16.

His knowledge of House procedures made him a natural to take over the role of conservative watchdog previously held by Iowa Republican H.R. Gross, who spent a lifetime battling Democratic spending measures.

But it was inevitable that Bauman would outgrow that. "Unlike H.R. Gross, Bauman is a very, very bright young man who has a great deal more intellectual latitude and a broader vision than H.R. Gross ever had," Rep. Edward Dewinski (R-Ill.) said.

Bauman is also benefitting from another situation-the discontent of some House conservatives, particularly the 35 freshman Republicans, with their leadership.

Freshman Republican Newt Gingrich of Georgia said many of the new Republicans look more to Bauman and Rep. John Rousselot (R-Calif.) for leadership than to elected leaders like Minority Leader John J. Rhodes of Arizona. "Rousselot and Bauman are the real leaders of the opposition party," Gingrich said. "They dominate the floor more than the real leadership does and sometimes they do it despite the Republican leadership."

Bauman, a frequent critic of House GOP leadership, said, "Creeping paralysis sets in. They have accepted the status of being in the minority for so long. They don't know how to capitalie on the conservative trend."

Some bloodletting among Republicans may come if Illinois Rep. John B. Anderson, the House Republican Conference chairman, runs for president of the Senate. If he does, he has said he would give up the No. 3 Republicabn leadership slot of conference chairman. Ohio Rep. Sam Devine, a conservative but bland veteran, would like the job. However, young members want a more dynamic leader and mention Bauman, Trent Lott (Miss.) or Bud Shuster (Pa.).

Asked what he would do if he were one of the Republican leaders, Bauman said he thinks it's time to attempt to revive the coalition of Republicans and conservative Democrats that dominated Congress in the 1950s and early '60s.

He says freshman Texas Democrats Marvin Leath and Phil Gramn are prime examples of conservatives who might join such a coalition.

In the next two weeks, when the implementing legislation for the canal treaties comes to the floor, Bauman will play a leading role.

One issue is cost. Bauman said he believes the treaties' actual cost to the taxpayers could be significantly greater than the administration's $4 billion figure.

Bauman said Panamanian leaders are demanding items not in the treaties - such as possession of all movable equipment and materials, retroactive tax jurisdiction over U.S. corporations in the canal zone, and renovation and repair of facilities - that could cost billions more.

While Bauman is as partisan a House member as exists, he has worked with Democrats, such as California Rep. Phillip Burton and merchant marine Chairman John Murphy of New York, who accepted many of Bauman's amendments to the Panama Canal legislation.

"Murphy was a prince. Maybe it was because I had 18 proxies in my pocket," Bauman said.

Bauman believes the treaty legislation will pass the House. But he says if the administration tries to change it significantly or reshape it to its liking in a House-Senate conference, it may fail on a final floor vote.

Bauman hopes to make the legislation objectionable enough to Panama that the country would reject the treaties and have to negotiate new ones.

Of the 1980 Senate race, Bauman says, "I don't have any present plans to run for Mathias' seat."

If Bauman is as smart as most people think he is, he's not likely to give up the relative safety of his House seat.

Maryland GOP Chairman Allan C. Levy said he hopes Bauman won't try "because he couldn't beat Mathias in a statewide race."

Rep. Majorie Holt, Bauman's Republican ideological twin in the Maryland delegation, said, "We talked every day and he'd keep saying he hasn't made up his mind but I really don't think he will."

Bauman said only a Democratic opponent such as former governor Marvin Mandel might make the race tempting. At 42, Bauman can afford to wait. CAPTION: Picture, no caption