With the November elections only a few weeks away, the heated political battle over control of the U.S. Senate continues to intensify.

The Democrats now control the Senate 50 to 49 to 1 - meaning a single-seat switch could put Republicans in the driver's seat. If such a change occurs and the House remains Republican, President Bush will have a much easier time making his ideas law.

In almost every midterm election (midway through the president's four year term), the president's party loses seats. And the numbers would seem to stack up against the Republicans. Senate elections are staggered so that a third of the 100 seats are up for election every two years. Of the 34 Senate seats up this election, 20 are held by Republicans and 14 by Democrats.

However, geography seems to favor the Republicans. Many of this year's races are in the South and Midwest - states captured by George Bush in 2000.

What's at stake

When Bill Clinton was sworn in as president in 1993, both the House and Senate were controlled by Democrats. Since he and the leaders of both houses of Congress were all in the same party, Mr. Clinton was able to push parts of his Democratic agenda until 1994, when both the House and Senate went Republican.

Similarly, when George Bush became president in 2001, Republicans controlled both houses of Congress. This made it easier to pass laws like the Republican tax cut. However, Mr. Bush's laid-back relationship with Congress ended a year later when Vermont Sen. Jeffords switched from the Republican party to become an independent, tipping control of Congress away from Republicans.

Suddenly there was a Democrat in charge of the Senate. Majority Leader Tom Daschle challenged the president on issues such as tax cuts, health care and social security, often making it harder for the administration to work with Congress.

The power of the committee

One of the most powerful aspects of the legislative branch is the committee structure -where most of the Congress' work is done. Laws are rarely passed without a committee's stamp of approval, and most policy disputes are resolved during committee consideration of bills.

When the balance of power in the Senate changes, the chairmanship of each committee switches to a member of the majority party. The chairman decides what to debate when. Those committees shape economic policy and even parts of foreign policy, like how much power Congress gives the president to wage war.

The Senate also confirms the president's nominees for federal judgeships. This confirmation power is felt in the makeup of the Supreme Court, where nine judges make the final decisions about high-profile cases, but also the lower courts, where hundreds of judges make thousands of decisions that frame values that shape life in America. These judges decide how easy or hard will it be for a woman to get an abortion, the balance between industry and the environment and the definition of civil rights protections.

Judges are appointed for life and their legacy can last much longer than that of the president, who can only serve eight years at most.

Races to watch

One of the year's most dramatic political battles is being waged in New Jersey. Until last month, the race was between the current senator, Robert Torricelli, and his Republican challenger, Douglas Forrester. Torricelli lost a lot of support when he was officially scolded for allegedly accepting illegal gifts. Feeling that the controversy was hurting his chances of keeping his seat, he withdrew from the race.

The Republicans said they would fight any attempts to replace Torricelli's name on the ballot. However on Oct. 7, the U.S. Supreme Court refused a Republican call to overturn a New Jersey court decision allowing Democrats to add a new candidate, former Sen. Frank Lautenberg, to the ballot in Torricelli's place.

Meanwhile, in the president's home state of Texas, a powerful Republican senator is retiring and the state attorney general, John Cornyn, is facing a spirited challenge from Democrat Ron Kirk, a former mayor of Dallas, who would become the nation's only black senator if he's elected.

And for those who remember the never-ending presidential election of 2000, such a debacle could happen again. In Louisiana, Republicans are trying to force incumbent Democratic Sen. Mary Landrieu into a runoff by fielding three candidates against her in the November election. If no one gets more than 50 percent, the two top candidates face off again in December - so we may not know who controls the Senate until Christmas!

--By Leah Clapman, NewsHour Extra