With control of Congress at stake and the election cycle closing in, the tension of the final campaign days is evident between the Senate campaign chairmen, who bickered Sunday over key issues motivating voters and who's going to win the Senate majority.

Sen. Charles Schumer, head of the Democratic Senatorial Campaign Committee, said the Nov. 7 election is a referendum on President George W. Bush.

"The more it becomes a referendum like that, the better we do. In fact, with the exception of one candidate, no other Republican candidate uses a four-letter word in his or her commercials, B-U-S-H. The Republican candidates don't use the four-letter word, Bush, in their commercials, because they're running away from him and they see this wind blowing at our back," Schumer told "FOX News Sunday."

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Democrats need to pick up six seats to take control of the Senate. Sen. Elizabeth Dole, who runs the National Republican Senatorial Committee, said the race isn't about Bush, who was out campaigning this weekend, but is not on the ballot. She said it's about national security, the economy and social issues.

"The Democrats are not going to take over the Senate," she said. "We're going to maintain the majority. But if they were to take over the Senate, it would weaken our economy, tax increases, it would weaken our security and it would weaken our shared values.

"Each candidate must speak to Iraq from his own conscience. Obviously, it's a major issue. There's no question about that. But what we're trying to do is find a way to win" the war, Dole said.

According to one Republican who played a lead role in the GOP takeover of Congress in 1994, the race is not about Bush or Iraq. In a tough op-ed piece in Sunday's Washington Post, former Republican House Majority Leader Dick Armey wrote that his party will lose control of Congress because "Republican lawmakers forgot the party's principles, became enamored with power. Now, the Democrats are reaping the rewards of our neglect — and we have no one to blame but ourselves."

According to RealClearPolitics poll averages, five Senate seats are currently considered tossups — Missouri, Montana, New Jersey, Tennessee and Virginia. RealClearPolitics says the polling now projects a Democratic pick-up of four Senate seats.

RealClearPolitics lists the Maryland Senate race as leaning Democrat, but several other nationally recognized political handicappers call that contest a toss-up. Republican Lt. Gov. Michael Steele has pulled into a dead heat in most polls against Democratic Rep. Ben Cardin.

"In Maryland, which they say is close, today, a Washington Post poll showed it 54-43 for Cardin. And, in the red states, we believe we're ahead in five, even in two and down by a little in one," Schumer said.

Maryland's race could turn on the African-American vote, which comprises 25 percent of the state's electorate, the highest percentage in the country.

Historically, Republicans have rarely won more than about 15 to 20 percent of that state's black vote. If Steele, the highest-ranking elected black politician in Maryland history, can win about 35 percent of the black vote in Montgomery and Prince George's counties, it will be nearly a mathematical impossibility for Cardin to win.

In other hotly-contested race, Republicans say they still have hope that incumbent Sens. Conrad Burns in Montana and Lincoln Chafee in Rhode Island have an outside chance to hold on against very strong challengers, John Tester and Sheldon Whitehouse, respectively. RealClearPolitics has the Rhode Island race in the "leaning Democrat" category.

Whether a power shift or not occurs in the Senate and House, the congressional election could be the most expensive ever for a non-presidential year. According to one study, the candidate, political parties and outside groups will spend about $2.6 billion, a lot of that coming in the final days.

Republican hopes are based on very guarded optimism, and none would be surprised to see Republicans lose enough seats to swing the majority. Weekly Standard Executive Editor Bill Kristol said what it will all come down to is the get-out-the-vote effort.

"Pulling the voters to the polls, repeated phone calls, neighbors knocking on your doors," Kristol told FOX News. "The voters also have to want to vote."

Kristol said part of the challenge for the Republicans is the intensity of Democratic support, which could translate to more Democratic voters going to the polls.

"That's worrisome for the Republicans, that could change in the next week," he said, adding that the odds for the Senate are "maybe 2-1 that it stays Republican."

FOX News' Carl Cameron and Julie Kirtz contributed to this report.