Denny Rehberg often wears cowboy boots while campaigning for the U.S. Senate, telling stories about his ranching background and bashing the “death tax” and “Obamacare,” characterizations popular with Montana’s rural residents.

To Democratic Sen. Jon Tester, the Republican congressman who wants to take his place is all hat and no cattle.

The race, one of a few that will determine which party controls the Senate in 2013, is drawing millions of dollars in political money from out-of-state interest groups. Republicans need a net gain of four seats — three if GOP candidate Mitt Romney wins the presidency, because his vice president could break a tie vote — to regain control. Eleven weeks from the election, Missouri, Montana, Nebraska, North Dakota, Virginia and Wisconsin represent their best chances for pickups.