Another 13 percent of the 232 likely voters surveyed were undecided. The poll, conducted for the Review-Journal by Washington, D.C.-based Mason-Dixon Polling & Research Inc., carries a margin of error of plus or minus 6.6 percentage points.

"The numbers clearly suggest it's a competitive seat. I'd say Porter is at a disadvantage," Mason-Dixon managing partner Brad Coker said of the poll results.

The race for Porter's seat is expected to be one of the most competitive in the nation in November.

A former Boulder City councilman and mayor and former state senator, Porter, 53, is seeking a fourth term in the House of Representatives. Titus, 58, a University of Nevada, Las Vegas political science professor and the leader of the Democratic minority in the state Senate, was the unsuccessful Democratic nominee for governor in 2006.

The district had historically been about evenly divided between Democrats and Republicans, but Democrats in recent months have built an advantage of more than 20,000 registered voters -- about 6 percent of the electorate.

Although the poll puts Porter a few points ahead, he shouldn't feel comfortable, Coker said.

"He's under 50 (percent). Even though he's ahead, that's a big warning sign," he said. "He's vulnerable, without question. He won by the skin of his teeth last time, and now he's running in an even harsher anti-Republican environment. That's going to be a tough fight for Porter."

Also spelling trouble for Porter in the poll was his constituents' view of his performance rating. Just 36 percent thought he was doing an excellent or good job, while 56 percent rated his performance fair or poor.

That was the worst performance rating in Nevada's five-member congressional delegation, worse than Sen. Harry Reid (43 percent excellent or good), Rep. Dean Heller (52 percent), Sen. John Ensign (56 percent) or Rep. Shelley Berkley (61 percent).

The poll found that though men favored Porter, 53 percent to Titus' 34 percent, women favored Titus, 50 percent to 37 percent.

Porter and Titus each won 76 percent of the vote from their respective parties, but while Porter won 16 percent of Democrats, Titus had the support of just 6 percent of Republicans. A large portion of Republicans, 18 percent, were undecided.

Porter also prevailed among independents, earning 51 percent to Titus' 36 percent, while 13 percent remained unsure who they would vote for. Coker said that would be the crucial vote in the election.

"The independent vote is where it's going to be won and lost," he said. "That's how Porter has won it the last couple of times. In this kind of anti-incumbent, anti-Congress, anti-Republican environment, that might be harder than usual for him."

A Porter spokesman said it was impressive that Porter was running as close as he was to Titus in the poll, considering the circumstances.

"These numbers speak to the competitiveness and the demographics that define Nevada's 3rd Congressional District," Matt Leffingwell said. He noted that the poll was conducted "in the wake of a massive surge in Democratic voter registration and unprecedented enthusiasm for the Democrats' caucus in Nevada."

A spokeswoman for Titus' campaign found the poll numbers encouraging.

"These are incredible numbers. They show the depth of Dina's strength in the district," Kirsten Searer of the state Democratic Party said. "She launched her campaign for Congress just six weeks ago and already has established one of the most competitive congressional campaigns in the country."

Searer predicted that Titus' share of the vote would only increase over the course of the campaign as the district is targeted by national Democrats, the presidential race and state legislative races.

Porter and Titus still must both be nominated by their respective parties in the Aug. 12 primary.

Porter faces two other Republicans, Carl Bunce and Jesse Law, in his quest for the nomination. Titus is up against fellow Democrats Barry Michaels, Anna Nevenic and Carlo "Tex" Poliak.

The general election will also be contested by an Independent American Party candidate, Floyd Fitzgibbons; Green Party candidate Bob Giaquinta; independent candidate Jeffrey C. Reeves, and Libertarian Party candidate Joseph P. Silvestri.

Contact reporter Molly Ball at mball@reviewjournal.com or 702-387-2919.