WASHINGTON -- To celebrate his 30th birthday, U.S. Rep. Patrick Murphy of Florida threw himself a campaign fundraiser. Then another. And another. And another.

The four events this spring helped make Murphy, a Democrat from Jupiter, one of the House’s top fundraisers, and he can’t let up.

Scraping out victory in the country’s most expensive and vicious House race of 2012 and at least interrupting the career of tea party hero Allen West in the process, Murphy faces another high-profile campaign that will test the delicate line he walks in a quintessential swing district.

It will also answer the burning question of whether voters like what they see in the young Democrat, who is trying to cultivate a bipartisan voting record, or if they had simply seen enough of the bombastic West.

“It’s a microcosm of House Democrats’ dilemma,” said David Wasserman, an elections expert with the nonpartisan Cook Political Report. “While the national Republican brand is historically abysmal, Democrats have more raw vulnerable seats to defend, and Murphy’s is a prime example.”

Another one of those seats is south of Murphy in Miami, where fellow freshman Rep. Joe Garcia will have a tough battle. Democrats, meanwhile, think they have a good chance at regaining a seat in the Panhandle, where two-term Rep. Steve Southerland is likely to face Gwen Graham, daughter of Bob Graham, the former governor and senator.

Nationally, Democrats seem unlikely to erase the GOP’s 33-seat advantage in the House. Midterm elections have been historically unkind to the party that controls the White House and tend to draw older, white voters who vote Republican.

In a bitter twist, the loss of a polarizing, campaign donation-attracting opponent may make it even harder for Murphy, one of only nine Democrats in the country to win a district that went for Mitt Romney over President Barack Obama. “His prospects of winning a second term are almost entirely dependent on Republicans nominating someone who is unpalatable to independent voters,” said Wasserman, who gives Murphy no more than a 35 percent chance of besting any generic Republican.

The GOP began targeting Murphy immediately after he won the District 18 seat, which includes portions of Palm Beach, St. Lucie and Martin counties, confident their voter registration advantage will benefit a less controversial candidate. Republicans make up about 38 percent of the electorate; Democrats 36 percent; independents 26 percent.

Most districts in the country are far more one-sided, the result of gerrymandering. It has pushed Democrats to the left and Republicans to the right, resulting in a Congress that rarely cooperates. “I’m lucky I’m in a seat where I can be myself,” said Murphy, a Republican until 2011.

His early fundraising success, pulling in more than $550,000 in the first quarter, has not scared off competitors. Three Republicans have entered the race already and at least that many are considering a run.

“It’s all out of my control. We have to do our job here,” Murphy said, projecting a nonchalance that belies his aggressive fundraising. He just went through one of the roughest campaigns in America and faces another one, but Murphy seems to be going out of his way to be bland.

Sitting in a sparsely decorated office across from the Capitol, a press assistant by his side, he offered flat lines about keeping his head down, focusing on local concerns like beach renourishment, and sloughed off a question about balancing elected duties with the intense pressures of nonstop fundraising. Asked about West, he said: “I certainly don’t spend much time thinking about him. My focus is on my job.”