Paul Hackett, an Iraq war veteran and popular Democratic candidate in Ohio's closely watched Senate contest, said yesterday that he was dropping out of the race and leaving politics altogether as a result of pressure from party leaders.

Mr. Hackett said Senators Charles E. Schumer of New York and Harry Reid of Nevada, the same party leaders who he said persuaded him last August to enter the Senate race, had pushed him to step aside so that Representative Sherrod Brown, a longtime member of Congress, could take on Senator Mike DeWine, the Republican incumbent.

Mr. Hackett staged a surprisingly strong Congressional run last year in an overwhelmingly Republican district and gained national prominence for his scathing criticism of the Bush administration's handling of the Iraq War. It was his performance in the Congressional race that led party leaders to recruit him for the Senate race.

But for the last two weeks, he said, state and national Democratic Party leaders have urged him to drop his Senate campaign and again run for Congress.

"This is an extremely disappointing decision that I feel has been forced on me," said Mr. Hackett, whose announcement comes two days before the state's filing deadline for candidates. He said he was outraged to learn that party leaders were calling his donors and asking them to stop giving and said he would not enter the Second District Congressional race.

"For me, this is a second betrayal," Mr. Hackett said. "First, my government misused and mismanaged the military in Iraq, and now my own party is afraid to support candidates like me."

Mr. Hackett was the first Iraq war veteran to seek national office, and the decision to steer him away from the Senate race has surprised those who see him as a symbol for Democrats who oppose the war but want to appear strong on national security.

"Alienating Hackett is not just a bad idea for the party, but it also sends a chill through the rest of the 56 or so veterans that we've worked to run for Congress," said Mike Lyon, executive director for the Band of Brothers, a group dedicated to electing Democratic veterans to national office. "Now is a time for Democrats to be courting, not blocking, veterans who want to run."

But Democratic leaders say Representative Brown, a seven-term incumbent from Avon, has a far better chance of toppling Senator DeWine.

"It boils down to who we think can pull the most votes in November against DeWine," said Chris Redfern, chairman of the Ohio Democratic Party. "And in Ohio, Brown's name is golden. It's just that simple."

Mr. Fern added that Mr. Brown's fund-raising abilities made him the better Senate candidate. By the end of last year, Mr. Brown had already amassed $2.37 million, 10 times what Mr. Hackett had raised.

Senator Reid did not reply to repeated requests for comment.

Asked about Mr. Hackett's contention that he had been pressed to leave the Senate race, a spokesman for Mr. Schumer, Phil Singer, said, "We've told both Sherrod Brown and Paul Hackett that avoiding a primary will make it easier to win the Ohio Senate seat, " but he added, "Obviously, the decision to run is Mr. Hackett's and Mr. Hackett's alone."

Mr. Brown declined to comment on Mr. Hackett's candidacy, saying that he was strictly focused on building his own campaign.

Democrats wanted to avoid a drawn-out primary, especially one that could get bruising with a tough-talking outsider like Mr. Hackett.

The Ohio Senate race is regarded as critical to Democratic aspirations to take back Congress in the fall. Aside from focusing on Senator DeWine, the Democrats also hope to win as many as eight House seats in Ohio and the governorship from the Republicans.

Ohio Democrats are hoping to exploit the larger problems plaguing the Republicans. State Republicans have struggled to distance themselves from Gov. Bob Taft, a Republican who cannot run again because of term limits and who was found guilty last summer of four misdemeanor ethics violations. Representative Bob Ney's still-unfolding role in the scandal over the lobbyist Jack Abramoff also looms over the state's Republicans.

Mr. Hackett said he was unwilling to run for the Congressional seat because he had given his word to three Democratic candidates that he would not enter that race.

"The party keeps saying for me not to worry about those promises because in politics they are broken all the time," said Mr. Hackett, who plans to return to his practice as a lawyer in the Cincinnati area. "I don't work that way. My word is my bond."

Jennifer Duffy, who analyzes Senate races for the Cook Political Report, said that part of what made Democratic leaders nervous about Mr. Hackett was what had also made him so popular with voters.

"Hackett is seen by many as a straight talker, and he became an icon to the liberal bloggers because he says exactly what they have wished they would hear from a politician," Ms. Duffy said. "On the other hand, the Senate is still an exclusive club, and the party expects a certain level of decorum that Hackett has not always shown."

Mr. Hackett was widely criticized last year for using indecent language to describe President Bush. Last month, state Republicans attacked Mr. Hackett for saying their party had been hijacked by religious extremists who he said "aren't a whole lot different than Osama bin Laden."

Though Republicans called for an apology, Mr. Hackett repeated the mantra of his early campaign: "I said it. I meant it. I stand behind it."

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