Election ScorecardWhere the midterm elections stand today.

Which party would control the U.S. Senate if the election were held today? The numbers below show the leaders based on averages of the most recent polls in each state. The "momentum shift" meter indicates statistically meaningful trends in recent polls of competitive races. How did we get these numbers and what do they mean?

Senate Race Summary for Nov. 6:
The contest to control the U.S. Senate may well come down to a photo finish, although the Democrats now face the tough task of sweeping all four remaining tossup races to win. New polls in the Maryland Senate race over the weekend moved that state into the tossup column. With just a few hours remaining until the voters head to the polls, here's where the most closely watched races on our scorecard stand:

Tennessee: A slew of new polls in the state have been all over the map in recent days, showing everything from a six-point lead for Democrat Harold Ford Jr. (by Democratic pollsters Hamilton Beattie) to a 12-point advantage for Republican Bob Corker (by Mason-Dixon Polling and Research). But the bottom line is that our last-five-poll average has moved in the last week from a dead-heat tie to a more than seven-point Corker advantage (51.2 percent to 43.8 percent), more than enough to classify Tennessee as "lean" Republican.

Maryland: Several new polls released over the weekend have narrowed Democrat Ben Cardin's last-five-poll average margin over Republican Michael Steele to just 3.8 points (48.4 percent to 44.6 percent), just close enough to move the race into tossup range.

Montana: In early October, Democrat Jon Tester held a 6.6-point lead over Republican Sen. Conrad Burns. That lead has gradually narrowed since and now stands at 3.2 points (48.8 percent to 45.6 percent), just narrow enough to qualify as a tossup.

Missouri: This state has been a virtually trendless tossup all along, and this final week proves no exception. Democrat Claire McCaskill now holds a lead of just 1.6 points (47.6 percent to 46.0 percent) over Republican Sen. Jim Talent. Missouri remains the tossup of tossups.

Virginia: Democrat Jim Webb has been the Democratic surprise of 2006. Boosted by Republican George Allen's early gaffes, he hung in against a barrage of Republican attack ads during September then surged forward in late October, when Democratic ads finally filled the Virginia airwaves. Virginia is now a tossup, with Webb now leading by just 1.4 points on our last-five-poll average (47.6 percent to 46.2 percent). But he has gained nearly seven points on the five-poll averages over the last month, picking up another 1.4 points in the last week.

So, to recap, Republicans now hold or lead in 49 seats; Democrats hold or lead in 47. The Democrats need a 51-seat majority to control the Senate (since Vice President Cheney will cast a tie-breaking vote for the Republicans), so they must win all four of the remaining tossup states: Maryland, Montana, Missouri, and Virginia. Not an easy task.

One final note: With this update, the big momentum meter that sits atop our scorecard has moved to point in the Republican direction. Up until today, our momentum meter captured trends over roughly the last 30 days in all of the 13 competitive seats, because that was roughly the span of most of our last-five-poll averages when we started. Momentum over the last month remains with the Democrats. However, as of today, we have adjusted the meter to consider just the trends over the last week, which have been decidedly Republican (owing mostly to GOP gains in Tennessee, Montana, and Maryland).

Click here for an archive of Senate Race Summaries.

Key Senate races:

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