The many senators running for president are showcasing endorsements from county commissioners, mayors, and former state legislators while mounting what seems to be, at best, a meager effort to win over the senators with whom the candidates work day in and day out.

On the Democratic side of the aisle, the candidacies of four well-liked senators have frozen the endorsement race there in a stalemate. Republican senators, for their part, seem to be in no rush to get behind one of their own, Senator McCain of Arizona.

Senators Clinton, Obama of Illinois, and Biden of Delaware each have the pledged support of his or her home state counterpart. Only Senator Dodd of Connecticut, who is at odds with Senator Lieberman, lacks that backing. However, the list of endorsements for Democrats goes no further, with no other senators stepping out to embrace one of their colleagues or anyone else.

“Nobody wants to have an awkward moment in the well,” one Democratic staffer said, referring to the area on the Senate floor where senators mingle as they cast their votes. “So many people are running for president that there’s a great potential for an awkward moment if you come out too early.”

A top aide to one Democratic hopeful said the lack of a broad effort to win over Senate colleagues also can be traced to the fear of being seen as part of what many voters regard as the entrenched political class in Washington. “All of these candidates are running against the idea of being a senator,” the aide, who asked not to be named, said.

Democratic staffers said Mr. Obama’s enthusiastic campaigning last year for Senate and House members has given him the political clout to forestall a wave of endorsements that Mrs. Clinton might have expected to pick up. Some politicians who might have given an early nod to the former first lady, such as Senator Boxer of California, are remaining neutral to avoid snubbing the political newcomer from Illinois.

“It helps senators say, ‘I’m just going to stay out,'” a professor of politics at the University of Virginia, Larry Sabato, said. “Why make enemies unnecessarily?”

A different dynamic is at work among Republicans. The only serious contender in the Senate, Mr. McCain, has the backing of nine of his colleagues. That’s an improvement on the four endorsements he landed in the 2000 race, but still far short of a majority of his party’s caucus. “It’s really not that impressive,” Mr. Sabato said.

Analysts said the major roadblock is not deference to the long-shot candidacy of Senator Brownback of Kansas but the Arizona senator’s history of rubbing some of his Republican cohorts the wrong way. “They’re the ones who have to work with him every day. Almost all of them have been irritated by him at one time over campaign finance reform or his commentaries on a wide variety of other subjects,” Mr. Sabato said. “He is unpredictable, and unpredictable people have difficulty working in a collegial body.”

Mr. McCain’s two leading rivals for the Republican nomination have scored some support in the Senate, even though they have never served there. A former Massachusetts governor, Mitt Romney, has the backing of four senators, including both of those from Utah, where Mr. Romney worked to stage the 2002 Winter Olympics and many resident share his Mormon faith. Mayor Giuliani has one senator in his camp, Senator Vitter of Louisiana.

Messrs. Romney and Giuliani tend to stress their support among House members. The former governor has 24 pledges of support there, while the ex-mayor has 14.

“Governor Romney is from outside Washington and so Congress is not his usual haunting ground. But we are happy with the support we’ve received so far and we plan to continue to build on our success,” a spokesman for Mr. Romney, Eric Fehrnstrom, said.

One Democratic operative, Jeff Link, said the focus of the endorsement race in the Senate and elsewhere is on political figures who hold unusual sway. “The premium is with those who fall into certain categories: key constituencies, early states, and for finance reasons,” he said.

Mr. Link was a top adviser to a former Iowa governor who recently quit the race, Thomas Vilsack. Senator Harkin of Iowa, who had promised to back Mr. Vilsack, now finds himself to be the subject of fresh entreaties from Mrs. Clinton and Mr. Obama, Mr. Link said. “They certainly go out of their way to chat him up on the Senate floor during votes,” the Democratic operative said. “They call him. … They’ve definitely been reaching out.”

Mr. Link, who has worked for Mr. Harkin and plans to do so again, said he expects the Iowa senator to keep his powder dry. “I don’t think he’s anxious to sort of pick sides right now. … He’s up in ’08 and his priority is to try and be a good host,” Mr. Link said.

A former senator from North Carolina, John Edwards, has no Senate endorsements but 13 in the House.

Mr. Biden’s deputy campaign manager, Evan Ryan, said he has spent little time trying to cajole colleagues. “This not about Washington. It’s about the primary states. Senator Biden’s energy is geared towards getting the support of primary voters,” she said.

At this point in 1999, President Bush had eight Senate endorsements. By January of the following year, 29 senators were on board.

In the previous Republican nominating contest, the Senate majority leader, Robert Dole of Kansas, far outpaced three of his colleagues, holding 22 Senate endorsements by June 1995 and 31 by the time of the New Hampshire primary, after the other senators quit the race.
This year, some of Mr. McCain’s colleagues have gone so far as to encourage other candidates to jump into the contest. Senator Corker of Tennessee and a former Senate minority leader, Bill Frist, are urging an actor and ex-senator from the Volunteer State, Fred Thompson, to mount a White House bid.

If the “Law and Order” star does run, his own history of endorsements could haunt him. In the 2000 contest, he effusively backed Mr. McCain. “When it comes to personal courage and integrity and the courage to do what he thinks is right, regardless of whether or not it’s particularly popular at the moment, John McCain has shown characteristics of leadership like no one else I’ve ever seen,” Mr. Thompson said, according to CNN.