WASHINGTON (AP) — Republican Pat Roberts held off independent businessman Greg Orman and put the GOP on the verge of taking control of the Senate.

Democrats can’t afford any losses in the five races that remain undecided in Alaska, Iowa, New Mexico, North Carolina and Virginia.

And they also must win a Dec. 6 runoff in Louisiana between Democratic Sen. Mary Landrieu and Republican Bill Cassidy.

Republicans picked up seats earlier Tuesday in Arkansas, Colorado, Montana, South Dakota and West Virginia.

WASHINGTON (AP) — Republicans are closing in on control of the Senate with the defeat of 

Republican Cory Gardner beat Democratic incumbent Mark Udall in Colorado.

Kentucky Republican Mitch McConnell won re-election earlier Tuesday. He would become majority leader if Republicans win the Senate.

Republican Mike Rounds won a Democratic-held Senate seat in South Dakota, the third of six the GOP needs for a Senate majority.  

The onetime South Dakota governor won a four-way race to replace Democratic Sen. Tim Johnson, who is retiring.

A closely watched race tonight will be the Senate race in Virginia, where Republican Ed Gillespie has a surprising early lead over ex-Gov. Mark Warner. 

With 40 percent of the vote counted, Gillespie is ahead 52 percent to 46 percent for Warner. Gillespie is a former chairman of the national GOP.

Republicans have also captured the Arkansas Senate race where Rep. Tom Cotton defeated two-term Democratic Sen. Mark Pryor after a heated and expensive race. 

Republicans have made major gains in Arkansas over the past two elections, primarily by trying to link Democrats to President Barack Obama, who lost the state in 2008 and 2012. 

Key contests remain undecided in Alaska, Georgia, Iowa, Kansas, North Carolina and Virginia.

And Louisiana Democratic Sen. Mary Landrieu is headed to a Dec. 6 runoff with Republican Bill Cassidy. 

Lamar Alexander won a third-term in Tennessee after branding Democrat Gordon Ball as “one more vote for Barack Obama’s agenda.” In Oklahoma, Republican Sen. Jim Inhofe was re-elected, while Rep. James Lankford won the election to replace Republican Sen. Tom Coburn, who is resigning.

In Mississippi, Thad Cochran, who endured a tough primary, won re-election. And Susan Collins won a fourth Senate term from Maine. 

Massachusetts Democrat Ed Markey and Democrat Cory Booker in New Jersey each won a first full term after winning special elections last year.

Earlier, Republicans picked up an additional Senate seat in West Virginia. 

Tennessee voters re-elected Gov. Bill Haslam, while Republican Robert Bentley won a second term as governor of Alabama.