Leaving the relatively comfortable confines of a House seat to run against a congressional colleague in the Senate is no easy decision to make, but the rewards can be plenty, and several members will try to make the leap in 2004.

"It's a big deal for House members to move to the Senate – it gives them a statewide base, and some people think it's the best job in politics," said Norm Ornstein, political analyst for the American Enterprise Institute (search).

In 2004, 34 Senate seats will be up for grabs, 19 of them now held by Democrats and 15 held by Republicans.

Five House members – Rep. Mark Foley, R-Fla., Rep. Pat Toomey, R-Pa., Rep. Joseph Hoeffel, D-Pa., Rep. Johnny Isakson, R-Ga., and Rep. Michael "Mac" Collins, R-Ga. – have already announced their candidacies for Senate. Some are competing for the same seat, which means that more than one House seat could turn over as a result of the Senate races.

In addition to the five declared candidates, Rep. Allen Boyd on Thursday said he is putting together a campaign team to pursue the Democratic nomination should Florida Sen. Bob Graham decide not to seek re-election. Graham is running for president.

If Graham steps down, Boyd could face in a primary Reps. Alcee Hastings and Peter Deutsch as well as other state and local Florida officials.

Others have also stepped into the fray. In Washington, Republican Rep. George Nethercutt has been named as a potential challenger to Democratic Sen. Patty Murray. In Nevada, Republican Rep. James Gibbons is being encouraged to challenge Democrat Sen. Harry Reid. Aides from both representatives' offices say their bosses don’t plan on making any announcements until the end of the summer.

Rep. Jim DeMint, R-S.C., has been raising money for months to run for the seat now held by Sen. Fritz Hollings, a seven-term Democrat. Hollings, who has frustrated some Democrats by keeping a lid on his future plans, has said that he wants to see if the party can field a credible candidate before he steps down.

Rep. Richard Burr, R-N.C., is expected to get the GOP nomination to run against Democratic Sen. John Edwards, who is running for the Democratic nomination for president, and like Graham, has not yet announced whether he will run for re-election or not.

Foley, currently serving his fifth term in the House, is also seeking to replace Graham to represent Florida, but could face a tough primary against former Rep. Bill McCollum, who lost a bid for the U.S. Senate against Democrat Bill Nelson in 2000. Rep. Dave Weldon, R-Fla., is also considering a run.

Early GOP polling finds Foley, who told Foxnews.com that he has raised $3 million for his bid, behind McCollum 30 percent to 18 percent.

"He has a tough slog – he's running against another former House member who knows how hard this is, and has the advantage of having statewide name recognition from running before," said Ornstein of AEI.

In Pennsylvania, Toomey, a conservative now serving his third term, is challenging Sen. Arlen Specter in the primary. Toomey said the moderate Republican senator, now serving his 23rd year in office, must go.

"The real underlying motivation is I want to advance the conservative agenda for America and for Pennsylvania," he told Foxnews.com.

Democrat Hoeffel, who is also serving his third term in the House, said he is running because he has "become increasingly frustrated with what I believe to be a very radical right-wing approach by Republicans who are running the White House, the Senate and the House of Representatives," and said he can make more of a difference in the higher chamber.

He is banking that both men will emerge politically bloody and exhausted from the primary, giving him the advantage he needs.

"He's hoping they will both knock each other out or they discredit each other," said Ornstein, who added that Hoeffel bears the burden of broadening his name recognition in a big state and raising enough money to challenge the seasoned Specter.

A primary between Isakson and Collins for the retiring seat of Democratic Sen. Zell Miller in Georgia promises to produce sparks, while Democrats have yet to announce a candidate.

The prospect of attaining the prestige and security of senator – who is one of 100 members, rather than one of 435 in the House, and serves six-year terms rather than two years at a time – has always enticed sitting members of the lower chamber, say experts. And from their seat, they have certain advantages including a donor base, some name recognition and knowledge of federal legislative issues.

"The big disadvantage is that you have a legislative record. Any opponent can easily go through the votes one–by-one and call them on it," said Ron Faucheux, editor of  Campaigns & Elections (search) magazine.

Possibly the biggest pitfall, said Ornstein, is "they have no safety net." Each will have to forgo running for their House seat to pursue their Senate dreams.

"It's a tough decision for them to make."

Foley said he would rather take the risk. Though his House seat is relatively safe from challenges at this time, "it's a greater risk not taking one."