Rep. Chris Van Hollen ended months of speculation yesterday by declaring that he will not be a candidate for the U.S. Senate next year, saying he wants to focus instead on raising his children and electing more Democrats to Congress.

Van Hollen (D-Md.), who had $1 million on hand for a possible bid, said he came to that conclusion while on vacation with his wife and three children in the Poconos over the Fourth of July weekend.

"This was a decision I struggled with," Van Hollen said. "I believe we could have waged an energetic and ultimately successful campaign, but I believe it was the right decision."

Van Hollen's announcement caps a behind-the-scenes effort by several top Democrats to keep him out of the race to avoid an expensive free-for-all for the Democratic nomination.

In March, Sen. Paul S. Sarbanes (D) announced that he would retire at the end of his term, creating the first open Senate seat in Maryland in 20 years.

Rep. Benjamin L. Cardin (D-Md.) and former U.S. Rep. Kweisi Mfume (D-Md.) quickly jumped into the race for the Democratic nomination. The nominee is widely expected to face Republican Lt. Gov. Michael S. Steele, who is being wooed heavily by national GOP leaders. Steele has formed an exploratory committee.

Van Hollen spent the past four months raising money and traveling the state to gauge his support.

Although Van Hollen would have entered the race with a strong base of Montgomery County and liberal supporters, Cardin's campaign took an unusually aggressive posture. The Baltimore area congressman rolled out several dozen endorsements and raised more than $1 million in his first nine weeks as a candidate, according to his campaign.

"I think from Day One, Cardin's aim has been to create a head-on situation against Mfume," said Keith Haller, president of Potomac Inc., a research and polling firm.

If Van Hollen had run for Senate, he would have had to curtail his role as co-chairman of the Democratic Congressional Campaign Committee's 2006 candidate recruitment effort. And as a father of three children ages 9 to 14, he said he worried about the "stress" a 15-month campaign would have on his family.

"I didn't want to look back years from now and regret that decision," said Van Hollen, who represents half of Montgomery and a small part of Prince George's County.

Van Hollen was counseled by some senior members of the party, including state Senate President Thomas V. Mike Miller Jr. (Calvert) and U.S. House Minority Whip Steny H. Hoyer of Southern Maryland, the dean of the state's congressional delegation, that there would likely be other opportunities if he took a pass on the race.

The seat of Sen. Barbara A. Mikulski (D) is up for election in 2010, when she will be 74.

"I don't want to put Senator Mikulski in an early grave, but . . . there's certainly going to be an opportunity in the future for someone as bright and well-qualified as Chris," Miller said.

Waiting also could enhance Van Hollen's position in the House, others suggested. "He's smart, energetic, aggressive and hails from a safe district," said Thomas F. Schaller, a political scientist at the University of Maryland Baltimore County. "Within a few years, there could be dozens of House Democrats who owe their political careers to him, and that kind of leverage will help make him a powerhouse."

Hoyer, an early Cardin backer, said Van Hollen's decision "will clearly be to Cardin's benefit."

"I am very pleased we will have a clearer Democratic primary," Hoyer said.

If Van Hollen had gotten in, he could have made it easier for Mfume to win the nomination merely by securing his base of support among African Americans.

In an interview yesterday, Mfume warned the Democratic establishment against rallying around Cardin. "I have said all along this is not going to be a coronation, although some may think that will be the case," said Mfume, former head of the NAACP.

Baltimore community activist A. Robert Kaufman also is a candidate for the Democratic nomination. Several other Democrats -- including Anne Arundel County Executive Janet S. Owens, Montgomery County businessman Josh Rales and Lise Van Susteren, a forensic psychiatrist and sister of Fox News personality Greta Van Susteren -- are mulling a Senate bid.

Van Hollen's decision to sit out a race bucks his political history. Since his election to the House of Delegates in 1990, Van Hollen has developed a reputation for relishing a tough political fight.

In 1994, he gave up his safe House seat to challenge incumbent state Sen. Patricia R. Sher (D-Montgomery), who helped elect him in 1990. Van Hollen, the son of a former ambassador, defeated Sher 3 to 1.

In 2002, Van Hollen ran against Mark K. Shriver, a Kennedy relative and state delegate with a nationwide following, for the Democratic nomination for Congress. Despite being vastly outspent, Van Hollen beat Shriver by 2,400 votes. He then went on to defeat eight-term incumbent Constance A. Morella (R).

If Van Hollen ran for the Senate, at least a half-dozen Democrats from Montgomery County were poised to run for his congressional seat next year. That jockeying is now on hold because Van Hollen intends to seek reelection.

"A large part of me feels relieved, because now it's a decision I don't have to make," said Sen. Brian E. Frosh (D-Montgomery), one of many politicians who were looking at Van Hollen's seat. "Others are probably thinking: 'Rats!' "

Rep. Chris Van Hollen (D-Md.) had $1 million on hand for a possible bid.