At stake is the leadership of both houses, although the Senate is more in play than the House thanks to simple math -- Republicans need fewer seats to gain the majority in the upper chamber and retirements have thrown some toss-up seats into play.
That doesn't mean senators in so-called "safe" districts are safe. Just ask conservative Mitch McConnell, the GOP leader in the Senate who faces a primary challenge from the right in Kentucky because he isn't conservative enough. In Kentucky, McConnell is challenged by businessman Matt Bevin in the primary.
Or to a lesser extent, ask John Cornyn of Texas, the No. 2 Republican in the Senate who is being challenged because he, too, isn't conservative enough by first-term U.S. Rep. Steve Stockman, who has been dogged by ethical questions concerning financial disclosures.
Of the Senate seats up for election or special election in 2014, 21 are held by Democrats and 14 by Republicans.
In the House, David Jolly claimed the Republican mantle to run for the seat held by Rep. Bill Young in Florida, but that meant the party had to invest more capital than it wanted in a race to retain the swing district against Democrat Alex Sink, whose political past is under a cloud from when she was Florida's chief financial officer. The matchup, once seen as an early test of Obama's signature healthcare legislation, the Affordable Care Act, could morph into a bitter, more local fight.
"It's an expensive problem to solve for a seat that's not a must-win," one national GOP strategist involved in House races told the Hill.
All of the House's 435 voting members are up for re-election as are five of the six at-large delegates representing the District of Columbia and U.S. territories who cannot vote on the floor when House meets as the House of Representatives.
Eleven of the lower chamber's Democrats who so far announced they won't return after the 2014 election are either retiring or running for other office, while 17 in the Republican camp are either retiring or running for another office.
House Democrats must have a net gain of 17 seats in November to reclaim the majority -- a difficult prospect for a midterm election in which the president has low approval ratings. But Democratic Congressional Campaign Committee Chairman Steve Israel, D-N.Y., raised $10.4 million so far. As of the end of November the DCCC banked $8 million more than the National Republican Congressional Committee.
The state party primaries begin in earnest March 4, when Texas Republicans and Democrats will elect their parties' candidates for statewide and congressional races, and culminate Nov. 4, when voters across the country elect their representatives in state Capitols and on Capitol Hill. The entire House of Representative sits for re-election every two years, while roughly a third of the Senate is up.
Democrats are expected to focus on income inequity to invigorate their base and pick up support from middle-class Americans fretting about the income gap between the middle class and the wealthy, the Christian Science Monitor reported recently. And they have some potential red-meat issues:
-- Senate Majority Leader Harry Reid tried -- and failed -- to clear a legislative hurdle to allow a vote on extending unemployment insurance for 1.3 million long-term jobless Americans whose benefits expired Dec. 28.
-- Senate Democrats, too, are looking to increase the federal minimum wage.
-- President Obama, when he delivers his State of the Union Jan. 28, is expected to reiterate a speech he delivered last month in which he said income inequality and declining upward mobility combined to become the "defining challenge of our time: making sure our economy works for every working American."
Republicans are looking to make economic conditions part of their 2014 message, too.
Republicans believe they can make political hay by exploiting the underlying weakness of the job market (the unemployment rate for December fell to 6.7 percent from 7 percent, but only 74,000 private-sector jobs were added) and arguing voters should expect a better economic recovery than what they're getting from President Obama's administration.
Republicans hope this argument, along with attacks on the healthcare law and its botched rollout, will be the right nudge for voters who typically disdain sitting presidents in their second terms, the Hill reported.
"It's going to be about the issue of jobs, and when you look at it, the American people have a right to continue to be asking, 'Where are the jobs?'" House Speaker John Boehner, R-Ohio, told reporters recently.
Boehner also seized on a GOP poll that suggests voters now blame Obama more than former President George W. Bush for the state of the economy, a critical shift in thinking from when Obama cruised to re-election in 2012.
The poll, conducted by Boehner ally David Winston, indicated in November, 41 percent of those polled blame the economic woes on policies of the past while 49 percent blame policies of the present, Politico reported. After the 2012 election, 53 percent blamed past policies and 44 percent blamed current policies.
"Barack Obama came into office blaming George W. Bush for the state of the economy and the lack of job creation," sources said, relaying to Politico what Boehner told the GOP caucus in a closed-door meeting. "For years, that pass-the-buck strategy worked. But at the end of last year, a turning point was reached. For the first time, a majority of Americans now say they believe the troubles in our economy are more the result of the policies of the present than the policies of the past."
Also, Gallup reported last week that more Americans, 42 percent, say they are financially worse off now than they were a year ago, despite a sustained, albeit sluggish, economic recovery that has lasted nearly five years.
Just more than a third of Americans -- 35 percent -- said their financial situation improved during the past 12 months while 22 percent said their financial situation remained about the same.
Results were based on nationwide telephone interviews with 1,018 adults conducted Jan. 5-8. The margin of error is 4 percentage points.