MIAMI (AP) - The contest between Democratic Senator Bill Nelson and Republican Rep. Connie Mack IV will be a critical race as Republicans try to regain control of the Senate, a battle that pits the son of a former senator against the man who took his seat.
    
Nelson is seeking his third term at a time when Florida is the largest tossup state in a tight contest for the White House. The money, time and resources being pumped into Florida by President Barack Obama and Republican Mitt Romney will have an influence on whether Nelson will be able to keep the seat he won in 2000 after Connie Mack III retired.
    
"Winning Florida for Mitt Romney will most likely mean that we will win the U.S. Senate race as well," said Republican National Committee Chairman Reince Priebus. "Ultimately top of the ticket matters. That's where the horsepower's at and it will drive almost everything down the ticket."
    
Both candidates are already using the top of the ticket in their campaigns. Mack has begun calling Nelson a "lockstep liberal" who consistently backs Obama's policies while Nelson is trying to tie Mack to Romney running mate Paul Ryan's budget proposal that makes changes to Social Security and Medicare.
    
"There's a huge contrast between the two of us - many, many things, but not the least of which is just the discussion of the last few days with the Paul Ryan pick - Medicare and Social Security," Nelson said Wednesday after both candidates easily won their primaries. "I don't think that's in the best interest of seniors and I don't think they're going to like that very much."
    
Democrats now hold 51 seats in the Senate, although two independents tend to vote with them. Republicans see Florida as a place where they can try to regain a majority and outside groups have already spent millions in attack ads against Nelson.
    
Nelson, though, has found a way to win even when Republicans at the top of the ticket have also won. In 2000, when George W. Bush beat Al Gore by 537 votes to win the presidency, Nelson beat then Republican Rep. Bill McCollum by more than 284,000 votes. Six years later, Nelson beat then Rep. Katherine Harris with more than 60 percent of the vote even though Republican Charlie Crist was elected governor with more than 52 percent of the vote.
    
"I always run my own race and I have always tried to make up my mind on the issues by what is in the best interest of our country and our state. When I agree with the president, I will support his position and when I don't, I won't," Nelson said. "I think people look at me as someone who stands up for our people in Florida and don't just broad brush me with a broad brush of a label."
    
Nelson has managed to maintain an image as a moderate and he's done well in north Florida counties that usually overwhelmingly support Republicans. Part of Mack's strategy will be to chip away at the moderate image by tying Nelson closely to Obama.
    
Every chance he gets, Mack calls Nelson a "lockstep liberal" who supports Obama's major policies nearly every time. He says Nelson was the deciding vote on Obama's health care overhaul and is doing nothing to preserve Medicare in the long term or to address the budget deficit.
    
"He voted for Obamacare, he's voted to raise taxes more than 150 times. He supports regulation, he supports big government," Mack said. "We want to balance the budget. Senator Nelson sits on the Budget Committee. They haven't passed a budget in the Senate for over three years. There's going to be a lot of things we can point to."
    
Nelson, who is normally mild-mannered, is already trying to let voters know that Mack is not his father. A campaign ad depicts the younger Mack as someone who feels a sense of entitlement, but doesn't have the experience or character for the job. It points out that before Mack was elected to the Florida Legislature, he worked for a company that planned promotions for Hooters restaurants. It also mentions a bar fight and road rage incidents Mack was involved in as a young adult.
    
Mack's father admonished his replacement in the Senate for his campaign tactics.
    
"As a dad, it hurts. I've been in politics a long time and I don't think I can recall a sitting senator who is acting the way he's acting," the elder Mack said after his son won the primary. "It's going to be, I hope, an issues-based campaign between now and November the sixth. The problems facing our country are enormous and it's unfortunate he's not taking the road where we have this kind of discussion.
    
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