Tea party favorites Rand Paul and Marco Rubio won their bids for the Senate Tuesday night and Republicans picked off Democratic-held Senate seats in Indiana and Arkansas in early returns that pointed to across-the-board gains for the GOP. Scattered returns from House races suggested Republicans would gain a substantial number of seats. Democrats lost races in Virginia and Indiana and almost three dozen were trailing in very early returns as Republicans set their sights on winning a net of 39 seats needed to claim the majority. Republican candidates were powered by a combination of anxiety over the economy and a significant shift in sentiment among independents, who were critical to President Barack Obama's 2008 victory and to the Democrats' takeover of Congress just four years ago. Sen. Blanche Lincoln, D-Ark., was the first senate incumbent to fall, losing to Rep. John Boozman R-Ark. Lincoln survived a tough primary in the spring, but was the underdog throughout the general election. In Kentucky, Paul easily defeated state attorney general Jack Conway, while in Indiana, former Sen. Dan Coats, R-Ind., scored an equally easy victory over Democratic Rep. Brad Ellsworth, D-Ind. Republicans also held their Senate seat in Ohio, where former Rep. Rob Portman, R-Ohio, cruised past Lt. Gov. Lee Fisher. One of the most prominent of tea party Republicans, Christine O'Donnell, lost her bid for the Senate in Delaware, as Democrat Chris Coons held the seat once occupied by Vice President Joe Biden. In New Hampshire, state attorney general Kelly Ayotte won her race in another GOP-occupied seat. In one of the pivotal races, Democratic West Virginia Gov. Joe Manchin held an early lead over Republican businessman John Raese. A Manchin victory would create a huge obstacle to the GOP's hopes of capturing the Senate. With the unemployment rate at 9.6 percent, economic issues dominated the voters' agenda Tuesday. More than six in 10 called the economy their top concern, according to preliminary national exit poll data. About nine in 10 see the economy as in bad shape and more than three times as many said they believe the economy is getting worse rather than better. About half of all voters said they were 'very worried' about the national economy and most of them were backing Republican House candidates this year. Just 44 percent of voters said they approved of Obama's performance as president, according to preliminary findings, with 55 percent saying they disapprove. Significantly more voters said their vote was a message of opposition to the president than a sign of support - 37 percent to 24 percent. The early exit polls showed how dramatically the makeup of the electorate has changed since Obama's victory two years ago. There were far fewer young voters - 10 percent Tuesday compared with 18 percent in 2008 - and the number of minority voters also declined. This development occurred despite a concerted effort by Obama and other leading Democrats to motivate those groups. Tuesday's electorate was also more conservative. In the preliminary data, conservatives made up 41 percent of all voters, up from 34 percent in 2008 and 32 percent in 2006. If that held up, it would represent the highest share of conservatives in exit polls back to 1972. The biggest switchup this year is among independents, with these swing voters favoring GOP House candidates by a sweeping 17-point margin. Four years ago, independents broke for the Democrats by a similarly wide margin. Democrats faced daunting odds from the start of the 2010 campaign - the president's party almost always loses seats in the first midterm and the party's gains in 2006 and 2008 increased the likelihood of a Republican bounce back. But as the election gathered force, the possibility of significant GOP gains grew. Since the end of World War II, there have been five midterm elections in which the president's party lost more than 40 seats. Democrats lost 66 seats in 1966, 56 seats in 1946 and 52 seats in 1994. Republicans lost 49 seats in 1958 and 43 in 1974. Republicans ran against the Obama agenda and, in many competitive districts, Democrats ran away from it. Republicans sought to nationalize the election as a referendum on the president, while Democrats preferred to make House races a choice between individual candidates. The campaign included high drama and low farce, a year in which virtually nothing seemed off limits, whether it was talk of witches, whores, mob bankers, liars or an Aqua Buddha. The term 'extremist' - thrown about with great frequency - seemed almost mild by comparison. The primaries included a series of surprises, especially on the Republican side. In half a dozen states, insurgent conservatives, many backed by tea party activists, upset establishment Republican candidates. More incumbents lost primaries than in any year since 2002, but the number - three senators, four House members and one governor - was still relatively modest. One of the first to fall was Sen. Robert Bennett, R-Utah, who never made it through his party's convention process. A conservative senator, Bennett was punished for his vote in favor of the Trouble Asset Relief Program that bailed out financial institutions and for his willingness to work across party lines. But one of those senators who lost a primary, Sen. Lisa Murkowski, R-Alaska, subsequently mounted a write-in campaign and was in the thick of the battle as the polls opened on Tuesday. If there was a defining symbol of the 2010 campaign, it was that of the tea party, a loose confederation of conservative activists who both energized and shook up the Republican Party. The tea party movement first raised its banner in the spring of 2009, protesting what its supporters saw as a dangerous expansion of government's intervention in the economy and a crippling rise in the federal deficit and national debt. Over time, Republican leaders found themselves trying to harness the best of the movement's energy while defending against what Democrats quickly labeled the extreme views of many of the tea party's favored candidates. The campaign for control of the House played out on one of the largest battlefields seen in modern times, with roughly 100 districts considered mildly to extremely competitive. Virtually all those districts were in Democratic hands as the day began. Many of those districts, however, were on relatively friendly terrain for the Republicans. Overall, there were 48 House districts in Democratic hands that were also won by Sen. John McCain, R-Ariz., in the 2008 presidential race. Of those, 43 were considered competitive. Freshman and sophomore Democrats were especially vulnerable, as many had won in swing or marginal districts in a pair of elections in which Republicans suffered severe losses. The GOP's magic number to take back control was a net gain of 39 seats, which was identical to the number of Democrats who won in 2006 or later and were in some degree of jeopardy. The battle for the Senate played out in both swing states and in states that tilted toward the Democrats, making the Republican challenge of picking up a net of 10 seats all the more difficult. Republicans were seeking to take Democratic seats in purple or even blue states, such as Pennsylvania, Connecticut, Illinois, Colorado, Nevada, Washington and California. The 2010 campaign was long, ugly and costly. Total spending, which includes that of candidates, Republican and Democratic Party committees and outside groups, approached $4 billion, by some estimates. Much of that came from unaffiliated groups who were not required by law to disclose their donors. That became a major point of controversy as Obama and other Democrats warned against the infusion of secret money from corporations and special interests influencing the outcome of the election and potentially the shape of new legislation next year. The outside money played a major role in many of the most competitive states, including those in Colorado, Nevada, Pennsylvania and Washington. Negative ads flooded television screens in states and districts with competitive races, sometimes so many that it was all a viewer could do to try to watch them. Democrats concluded early in the campaign that their best hope of preventing sizeable losses was to demonize Republican challengers. But Republicans, through their party committees, engaged in just as many negative attacks. Polling director Jon Cohen and staff researcher Alice Crites contributed to this report. 