A handful of key Senate races are likely to determine control of the chamber this fall. Some of the closest contests are heating up after candidates in Texas, Nevada, Pennsylvania and Wisconsin took the debate stage this week to make their case to voters. Currently, there are 49 Republicans serving in the Senate, 48 Democrats and three Independents who caucus with Democrats, effectively giving the party a 51-49 seat majority. As Democrats defend their slim edge in the upper chamber, political analysts say it’s going to be an uphill climb. “I think Republicans are going to win the Senate. They have a much clearer path,” said Todd Belt, director of George Washington University’s Graduate School of Political Management. “Democrats have many more seats that they have to defend than Republicans do. You can take one off the board for Democrats right away, and that’s West Virginia.”West Virginia Sen. Joe Manchin …