Sen. Bill Nelson of Florida defeated Republican Connie Mack on Tuesday to win a third term and help Democrats try to hang onto control of the U.S. Senate.

Nelson won even though he was up against a sitting congressman whose father once held the Senate seat -- and whose great-grandfather was a baseball Hall of Famer.

With more than 4.5 million votes counted, Nelson had 55 percent of the vote compared with Mack's 42 percent.

The race was more of an afterthought compared with the battle between President Barack Obama and Republican Mitt Romney.

Even some within Mack's own party predicted he needed a big Romney victory in Florida because Nelson has a history of success even when Republicans prevail in other top races on the ballot. Early returns showed the presidential candidates basically splitting the vote in Florida.

Independent voter Milly Herrera was one of those who supported Romney and still cast a ballot for Nelson.

"There are some issues where I support the Democrats and then there some issues, like small business and the economy, where I would support the Republicans," she said.

There was a high turnout expected in Florida, where more than 4.5 million people -- about 38 percent of the electorate -- had already voted before Election Day.

Mack, 45, represents southwest Florida in Congress. He announced a year ago he would seek the seat his father held before retiring in 2001.

Mack consistently beat the theme that Nelson supported Obama with nearly every vote, including the president's health care overhaul and the $787 billion federal stimulus.

Meanwhile, Nelson quietly raised more than $16 million compared with Mack's $6 million, and spent some of it trying to tear down Mack's reputation through television ads. He depicted Mack as a bar-brawling party- boy who planned promotions for Hooters and had a hard time paying bills when he was going through a divorce. The ads referenced incidents Mack was involved in during his early 20s.

Nelson, 70, flew on a space shuttle mission while in Congress, and is a strong proponent of the space program. He co-sponsored legislation in 2010 that lays a foundation for continued space exploration.

For a senator with a target on his back, he didn't spend much time in public making a case for his re-election.

Mack tried to make a splash in this race whenever he could. He made sure he was with Romney or running mate Paul Ryan when they made one of their frequent visits to the state, knowing his fortunes were tied to the top of the ballot.

He called for more debates after the candidates only got together once. Their hour-long debate was held before prime- time and gave the candidates little time to detail how they would address the rising cost of Medicare and Social Security, the budget deficit and health care. It was more of a name-calling, finger-pointing debate than a discussion on federal policy.

Mack spent the last three weeks traveling thousands of miles around the state by bus, though he spoke before mostly small crowds, often times just 20 or 30 people.

Nelson held only a couple of events. He attended a press conference Saturday calling for an extension of early voting, and on Monday, he waved signs in Orlando, where he lives, and in Melbourne, where he grew up. He also made an appearance with first lady Michelle Obama.

At Mack's election party, James Doerning, 65, of Cape Coral said he knows Mack will do well in southwest Florida, but he noted Nelson is from Orlando, a key area in the state to win.

"I like his father a whole lot," Doerning said of Mack. "I think one of the biggest things going for him is his age compared to his opponent."

Nelson's remarks are as follows:

"Good evening, Florida. I am thankful to the Lord, and, I am humbled by the support of the people of Florida.Grace and I are grateful for this continued privilege of public service.

I 'd also like to start by thanking Grace, our son Bill Jr., our daughter Nan Ellen, and her husband Mike for their support and love. I'd also like to thank my very talented staff and the many, many campaign supporters.

I'd also like to say that Connie Mack was my opponent -- not my enemy.You know, these days the extremists in our political system try to divide. We need to unify.

Far too many other folks in Washington remain blindly focused on a rigid, partisan agenda.You cannot get anything done that way.And we've all seen the result of gridlock: Nobody wins.

So, I promise tonight to continue to try and break that partisan gridlock. I promise to continue to try to build consensus.I promise to keep my hand extended across the aisle and to work with anyone, Republican, Democrat or Independent, to get things done for the people of Florida, and our country.

That's the special trust that a public servant has.

You've given me the privilege of a lifetime of public service, first in the Florida Legislature, then in Congress, then as a state Cabinet member, and now, with a third term in the U.S. Senate.

We have the opportunity to help solve some of the most pressing challenges ever facing our nation.

We must protect and preserve Medicare and Social Security. A lot of folks want to get rid of them. I don't.

We need to get our energy costs down.That's going to take real commitment to developing alternatives to oil.And I want Florida to be a leader in renewable energy.

We also need to keep growing our economy.

That's going to take a real commitment to protecting and expanding the middle class, primarily by helping the private sector put people back to work.

All the economic indicators say the U.S. economy is improving. And it is.But many folks in Florida haven't seen the economy recover fast enough.

And it won't fully recover until we restore some fiscal sanity to the federal government, which means cutting wasteful government spending, balancing the budget and making sure billionaires don't pay a lower tax rate than the rest of us.

We've certainly been though a lot together here in Florida. But it's when we face tough times that I'm most reminded of what gets us through – our faith, our family, and our community.

Faith, Family, Friends…

And it's the people all across Florida who inspire me, the people I'm talking about when I talk about standing up and fighting for Florida.I always have and I always will.

God bless you. And God bless America.

The statement from Fla. Democratic Chair Rod Smith is as follows:

"On behalf of Florida Democrats, I wish Sen. Bill Nelson congratulations on his re-election. Sen.Nelson has and will continue to serve our state and country with the highest level of distinction.

Throughout this campaign and his entire career in public service, Sen. Nelson has stood up for the values that make our state great. He is a true champion for middle-class families and a passionate advocate for our state.

He has delivered for the people of Florida, and tonight they have delivered him a decisive victory."