Credit: senate.gov

Key Senate races in Virginia, Connecticut, and Massachusetts could determine which party controls the Senate. Independent voters may be the most important voting blocs in all these races.

VA Senate race between Tim Kaine (D) and George Allen (R)

A race between two former governors in an important swing state shows how pivotal independents can be especially when it concerns the balance of power in the Senate. Sen. Jim Webb (D-Va.) leaves behind an open seat that is the prize between Tim Kaine and George Allen. To quantify how close the race is, look at two recent polls, each showing the direct opposite impact for Independent voters.

Public Policy Polling president Dean Debnam states the race as "toss up" but the July poll shows "It is among Independent voters where Kaine finds his advantage, leading Allen among them by a 45-37 margin." Although a Quinnipiac University poll shows George Allen with the edge. Notice the 8 percentage points going both ways.

Allen does have an edge with one key voting bloc, however. Allen has an 8 percentage-point lead over Kaine among independent voters. Allen even leads among independent female voters, whom Kaine has been trying to win over by insisting Allen would curb women's reproductive rights -- a strategy very similar to the one Obama is using against Romney.

CT Senate race between Chris Murphy (D) and Linda McMahon (R)

Linda McMahon lost a 2010 race for Senate. She has reshaped her image to appeal to more voters in a traditionally blue state. This could lead to an upset.

McMahon, a millionaire, infused millions of her own money into a 2010 race to fill Sen. Dodd's vacant seat and is doing the same now in 2012 in hopes of replacing retiring Sen. Lieberman. According to a Quinnipiac poll, she leads her opponent, Rep. Chris Murphy, among Independents 55% to 40%. On top of that, McMahon is gaining ground among women, trailing Murphy by only 4 points, 50% to 46%. This was a far different picture in 2010.

In McMahon’s failed 2010 Senate run against Sen. Richard Blumenthal, Democrats attacked World Wrestling Entertainment Inc., the league she co-founded with her husband, Vince, as violent and misogynistic. Those charges hurt her reputation among women and independent voters.

MA Senate race between Elizabeth Warren (D) and Scott Brown (R)

Massachusetts has a long history of voting strongly Democratic, but in 2012 the Senate seat formerly held by Ted Kennedy may remain in Republican hands. Moderate Republican incumbent Scott Brown is touting his record of agreeing with President Obama to court Democrats and still maintain a solid Republican base.

Independents have been an important group in the Scott Brown/Elizabeth Warren race all summer. Scott Brown has not always voted with his Republican colleagues and claims to be beholden to nobody except the voters. That centrist stance has helped him garner support from Massachusetts Democrats and Republicans alike.

Independent voters bolster Brown's lead, supporting him over Warren by 58 percent to 32 percent. The first-term senator also appears to have some crossover appeal: 20 percent of Democrats back him while 73 percent back their party’s nominee. Warren pulls 7 percent of Republicans, while Brown takes 97 percent.

Warren's attempt to paint Brown as a partisan Republican doesn't seem to be working, especially after Brown voted with the Democrats to pass financial reform legislation that Warren was such a pivotal advocate for.