Sen. Ben Nelson (D-Neb.) rebuffed solicitations by at least two senior Republican Senators to switch parties following the November elections at about the same time the White House was courting him to be the next Agriculture secretary.

Nelson, one of the most vulnerable Senators up for re-election in 2006, faces a drastically different political environment at home now that the man considered his likely Republican challenger, Gov. Mike Johanns, has been nominated for the Agriculture post.

Shortly after Election Day, Majority Leader Bill Frist (R-Tenn.) and Rules and Administration Chairman Trent Lott (R-Miss.) made separate appeals to Nelson asking him to join the GOP before he faces voters for a second term in a solid Republican state, sources said. The conversations were described as a “soft sell,” according to one Nelson confidante, who spoke freely about the discussions on the condition of anonymity.

“If you want to become a Republican, we would still want to talk to you about it,” said the Nelson confidante, paraphrasing the conversations the Nebraska Democrat had with the two GOP Senators.

But the talks never reached the level where the Republicans offered Nelson a specific incentive to switch parties such as a committee chairmanship or an offer to help with his reelection in 2006, one source said. Nelson turned down an offer last month by White House political strategist Karl Rove to be the next Agriculture secretary.

The Washington Post reported in Friday’s edition that while Nelson was not interested in heading the Agriculture Department, he would consider becoming the secretary of Commerce or Energy. A source confirmed the Post account Friday afternoon but said those conversations never went any further.

The news of Republican overtures to Nelson comes after Johanns, the man considered the Senator’s biggest threat for re-election, was nominated Thursday by President Bush to replace current Agriculture Secretary Ann Veneman. It is unclear if Lott or Frist spoke about the possibility that if Nelson switched parties, he could have faced a primary challenge from Johanns. Nelson’s spokesman denied rumors that Johanns’ nomination was part of a larger political plan to persuade Nelson to switch parties.

“Senator Nelson has no intention of switching parties, but he is flattered to be wanted,” said David DiMartino, Nelson’s spokesman. DiMartino would not address whether Frist and Lott reached out to the Senator.

Bob Stevenson, a spokesman for Frist, said he was unable to “confirm” the Nelson conversation.

“But I know Senator Frist thinks very highly of Senator Nelson,” Stevenson said.

With Nelson seemingly content to remain in the Democratic Party and run for re-election in 2006, Johanns’ selection has forced a major rethinking among Republicans about who should be the standard-bearer against the freshman Senator.

The preferred choice now is Rep. Tom Osborne (R), who until the Johanns announcement was seen as the governor-in-waiting in 2006.

Lt. Gov. Dave Heineman (R) will now serve out the final two years of Johanns’ term, and early indications are that he plans to seek a full four-year term of his own in 2006.

Heineman must appoint someone to fill his slot, and the wishful thinking among Democrats is that the choice could be Osborne.

Erin Hegge, a spokeswoman for the popular former coach of the University of Nebraska football team, said that the elevation of Johanns changes the political calculus for Osborne.

Hegge said that while Osborne had only been considering a gubernatorial bid, he will now also weigh the possibility of a challenge to Nelson.

“This is a new development coming from [Thursday’s] announcement,” Hegge said. She added that Osborne’s decision on his political future is not likely to be made before the middle of 2005.

Rep. Lee Terry (R-Neb.), who was mentioned as a Senate candidate but removed himself from consideration late last week, said that “people are going to wait for Tom to decide.”

Nelson is likely to take that time to strengthen his political base and add to his financial war chest.

As of Sept. 30, Nelson had $807,000 on hand.

Democrats pointed out that Osborne has made no secret of his distaste for Washington, D.C., and his desire to return to the Cornhusker State. A Senate bid would not seem to jibe with that plan.

Even Terry acknowledged that Osborne “has never said anything about the Senate.”

“A lot of his friends would like him to run for governor and be in Nebraska,” Terry added.

DiMartino sought to paint the developments as unalloyed good news for the Senator’s quest for a second term.

“What happened [Thursday] sent the Republican Party in Nebraska into a tailspin,” he said. “No matter who runs against Senator Nelson, he is prepared and excited to defend his record on promoting Nebraska values in the Senate.”

Aside from Osborne, state Attorney General Jon Bruning, state Republican Party Chairman David Kramer and businessman Dave Nabity have also been mentioned as GOP Senate candidates.

Bruning and Nabity had been angling for the governor’s mansion but may rethink their plans. Bruning told the Lincoln Journal-Star last week that “Ben Nelson is beatable after his very close 2000 race.”

“That’s something many Republicans have to consider, including me,” he added.

Nelson won his seat in 2000 by defeating then-state Attorney General Don Stenberg (R) 51 percent to 49 percent.

It was his second Senate bid; as a sitting governor in 1996, Nelson was defeated by now-Sen. Chuck Hagel (R) in an open-seat race.

Nebraska is one of the most Republican states in the country. President Bush carried it by 33 points on Election Day.

Democratic media consultant Karl Struble, who handled the television strategy during Nelson’s 2000 campaign, said that without Johanns in the race, the Senator goes from a “slight favorite” to a more solid bet.

“He represents the state very well and would be difficult to beat,” said Struble, before adding: “It is still Nebraska and it is still a red state.”

In the Senate, the efforts to try to lure Nelson away from the Democratic Party demonstrate how aggressive Republicans have become in trying to build their majority through recruitment and assuaging disaffected GOP Senators.

When Sen. Lincoln Chafee (R-R.I.) considered quitting the GOP last month, Frist and Senate Majority Whip Mitch McConnell (R-Ky.) assured him they would help him win re-election in 2006.

The GOP will control the Senate by a comfortable margin in the 109th Congress, 55-44, with one Independent who caucuses with the Democrats. But Republicans are still short of the 60 votes needed to break a filibuster.

“We still have our eyes on the magic number, which is 60,” said a Republican leadership aide.