Eleven of the U.S. Senate seats up for grabs this November are considered "toss-ups" by The Washington Dispatch, with Republicans in control 44 seats and Democrats in control of 45 (including independents who caucus with the Democrats).
Based on prior election results and The Washington Dispatch's comprehensive analysis of state polls, the Republicans are currently projected to end up with 48 Senate seats and the Democrats are currently projected to end up with 52 seats.
Of the eleven "toss-up" races, Republicans currently lead The Washington Dispatch Poll of Polls in four of those races: Indiana, Montana, Nevada, and North Dakota. Democrats currently lead in Florida, Virginia, Wisconsin, Connecticut, Missouri, Massachusetts, and Ohio.
The lone change from last week's projection is Massachusetts, where Elizabeth Warren (D) has retaken a small lead over incumbent Scott Brown (R).
The one positive sign for Republican Senate hopes is that in key swing states, Mitt Romney's surge in the polls is finally beginning to show some sign of a "coat-tail" effect for Republican Senate candidates. Democratic leads in Florida, Ohio, and Virginia all shrunk over the past week, especially in Virginia where George Allen (R) is now withing a half a point of Tim Kaine (D).
Rather than simply averaging the overall result of major swing-state polls pitting Senate candidates against one another (as is done on sites like Real Clear Politics), The Washington Dispatch digs into the cross-tabs of data behind major polls (those that freely publish the necessary data breaking down responses by party identification), and averages each candidates' share of the vote among Republicans, Democrats, and Independents. Then, these shares are applied to the actual turnout by party identification in each state (as measured by CNN's comprehensive exit polling in 2004, 2006, 2008, and 2010) for the past four national elections. To calculate poll numbers for each race for purposes of The Washington Dispatch's Senate projections, each candidates' average share of the vote by party affiliation is applied to the average turnout by party affiliation in each state over the past four national elections.