Republican Sen. Chuck Hagel of Nebraska won't endorse either Barack Obama or John McCain in the 2008 presidential election, a spokesman told FOX News on Wednesday.

Hagel has said previously that he wasn't going to get involved in the election, though last month he traveled with Democrat Obama to Afghanistan and the Middle East as part of a congressional delegation.

"Senator Hagel has no intention in getting involved in any of the campaigns, and is not planning to endorse either candidate.  He will be in Central and South America during both conventions on official travel.  Senator Hagel is focused on his job serving the people of Nebraska as a United States senator," said Hagel spokesman Jordan Stark.

The comment follows concerns raised by partisans in both parties over the prospect that Hagel, an Iraq war opponent, could be a potential running mate for Obama. The idea rubs many the wrong way.

"His anti-war posture might be attractive to Obama, but he's anathema to much of the progressive base of the Democratic Party," said Toby Chaudhuri, communications director for the liberal Campaign for America's Future.

Republican lawmaker Adrian Smith called the pairing "not a good fit" and said that on issues other than the Iraq war, Hagel and Obama are not compatible. The American Conservative Union, which examines voting records on everything from abortion to national security, pegs the Nebraska Republican as a conservative.

Plenty of people have suggested that Obama recruit Hagel, a Vietnam War veteran because they say he would help temper perceptions that Obama is too liberal and not adequately prepared for foreign policy challenges. A bipartisan ticket would also support Obama's call for breaking away from polarizing politics.

Others don't see Hagel in that role, and some predict that delegates to the party convention might not either.

"I think, though it is impossible to predict with absolute confidence, that the delegates would not deliver their votes unless at a minimum he switched political parties," said former Sen. Bob Kerrey, a Democrat from Nebraska. "Even then it would be a difficult vote."

Vic Covalt, who takes over as chairman of the Nebraska Democratic Party in December, said he's not fooled by Hagel's Iraq position.

"He's not a good man when it comes to everything else, and he hasn't voted well in any way, shape or form that would gain any support from me or any other thinking Democrat," Covalt said.

Nebraska Attorney General Jon Bruning, a Republican, questioned whether Hagel could take his place behind Obama.

"Hagel couldn't keep his mouth shut long enough to be somebody's No. 2," Bruning said.

"Hagel is his own man," he said. "It's tough to be someone's No. 2 when you're used to making your own decisions."

Although Hagel disagrees with President Bush and McCain on the war, he chafes at suggestions that he is less than conservative, pointing to his desire to reduce the scope of the federal government and give more control to states and cities. He says abortion should be allowed only when the life of the mother is in danger.

Yet in June, the Nebraska Republican said he would consider serving as Obama's running mate. Still, he added that no one had approached him about the job and that he expected Obama to pick a Democrat.

Hagel considered his own presidential bid but then announced last year he wouldn't seek a third term in the Senate or the Republican presidential nomination. He was widely mentioned as a running mate on an independent ticket with Michael Bloomberg before the New York mayor decided not to run.

Last month, McCain said Hagel could have a place in a McCain administration. Both are Vietnam veterans wounded at war, both labeled mavericks for speaking their minds and both strongly conservative in their voting records.

Still, Hagel hasn't endorsed the man he calls a friend and appears to be drifting farther from him. Since traveling to Iraq and Afghanistan with Obama, he has chided McCain for suggesting that Obama decided on a withdrawal from Iraq based on political expediency.

"John's better than that," Hagel said on CBS' "Face the Nation." "It's just not responsible to be saying things like that."

Hagel was on the short list for vice president once before, in 2000 as a possible running mate for George W. Bush. Hagel said at the time that he spent $15,000 on accountant fees to put together the information requested by the Bush campaign and interviewed twice with Dick Cheney, who was supervising Bush's search for a running mate.

Bush eventually picked Cheney.

FOX News' Trish Turner and The Associated Press contributed to this report.