Candidates, both political parties and hordes of corporate, labor, ideological and other groups have spent a record $1.1 billion on House races since this campaign cycle began last year, according to data compiled by the nonpartisan Center for Responsive Politics. Yet by the time the last votes are counted Tuesday, Democrats may pick up a handful of districts but are widely expected to miss their goal of gaining the 25 additional seats they need to grab control of the chamber.
-The redrawing of congressional districts to reflect the new census. Both parties protected incumbents but Republicans shielded more.
-A preponderance of at-risk Republican-held seats that the GOP offset with extra financial muscle.
-A close presidential race that has prevented either party from gaining a sweeping coattail advantage.
-Overarching national issues have not tilted the playing field to one side or the other.
"First and foremost it's redistricting," said Democratic pollster Dave Beattie, citing how GOP-led state legislatures were able to redraw congressional maps. "Institutionally, they were able in a redistricting year to protect the House gains they made in 2010," when Republicans captured House control.
Like most years, the vast majority of both parties' incumbents are likely to win. The percentage of victorious House members seeking re-election has dipped below 90 percent only twice since 1974 - in 2010 when the GOP stormed into control and 1992, when Democrats were hurt by a scandal involving the House post office.
Out of 435 House seats, around 60 are seriously competitive this year. About three dozen are currently held by Republicans and two dozen by Democrats. A handful of others are either new districts with no incumbents or races in which current House members are squaring off against each other.
In districts from one ocean to the other, Democrats have accused Republicans of trying to gut Medicare, the popular health insurance program for the elderly, and slice domestic programs like education while seeking tax cuts for the rich. They've also accused them of attacking women's rights with measures to curb abortion and cut funds for Planned Parenthood.
"Is he representing you?" asks an ad by the House Majority PAC, a political committee steered by House Democratic leaders, that attacks Rep. Brian Bilbray, R-Calif., for his votes on Medicare and other health issues.
The GOP has lambasted Democrats for supporting President Barack Obama's health care overhaul and other big spending programs like Obama's economic stimulus package. Democrats also are accused of cutting Medicare themselves and boosting taxes on the middle class.
"He is out of touch with central New York," an ad by the House GOP campaign committee says of former Democratic Rep. Dan Maffei, who is seeking to return to Washington. The spot faults Maffei for businesses leaving the district.
Through October, the GOP has enjoyed the spending edge.
Current House GOP candidates have spent $500 million from their own campaigns, reinforced by $99 million from outside groups like American Crossroads and $65 million from the House Republican campaign organization, according to the center.
Democratic candidates have spent $374 million, plus $71 million from outside groups like the Service Employees International Union and $61 million from the House Democratic campaign committee.
Added together, that's given the GOP the upper hand by $664 million to $506 million.
Among those targeted by outside groups: Orlando area Rep. Daniel Webster, R-Fla., the focus of $1.1 million in ads being run by Independence USA PAC, a political action committee run by billionaire New York City Mayor Michael Bloomberg, an independent.
"It's Michael Bloomberg coming in from storm-ravaged New York. I don't think in our district that if that were known that would play very well," said Webster campaign consultant Kirsten Borman.
The American Action Network, affiliated with House GOP leaders, launched an ad attacking Webster's Democratic rival, former Orlando police chief Val Demings, for supporting Obama's health care revamping.
Mitt Romney recorded a TV spot for Republican House hopeful Mia Love of Utah, where the GOP presidential candidate is overwhelmingly popular. "I trust Mia to protect seniors," Romney says.
Those in uncertain races include about two dozen House GOP freshmen from the 87-strong class of newcomers whose rise to power was energized by tea party voters. Among them is Rep. Scott DesJarlais from central Tennessee, a physician and abortion foe whose re-election seemed assured until recent reports that he once pressed a mistress to have an abortion.
The nation's most expensive competitive House campaign: freshman GOP Rep. Allen West's re-election battle in South Florida against Democrat Patrick Murphy, which has seen $17.2 million in spending. West, a firebrand conservative and prolific fundraiser, has spent $13.8 million of the total.
Republican pickups of three seats are possible in New York and likely in North Carolina, where three veteran Democrats are retiring following redistricting, further trimming the roster of both parties' moderates in Congress.
The GOP is also hoping to knock off Democratic incumbents in California and win other seats in Utah, Arkansas and Oklahoma. They could even defeat Massachusetts Democrat John Tierney, beset by a gambling scandal that has involved his wife and two brothers-in-law. Massachusetts hasn't had a House GOP member since 1997.
Democrats are hoping for big days in California and Illinois and their own pickups in New York - states where Obama is expected to win decisively. Especially in New York and Illinois, redistricting has not helped tea party-backed Republicans like Illinois Rep. Joe Walsh and New York Rep. Ann Marie Buerkle.
Reflecting areas in play, Democratic and GOP political groups have poured money in recent days into House races in Arizona, Minnesota and Rhode Island in addition to California, Illinois and New York.
Contests that pit two members of Congress against each other are often among the most bitter and costly. This year is no exception.
In Los Angeles, a pair of veteran Democrats - Reps. Howard Berman and Brad Sherman - argued nose-to-nose at a debate last month until they were separated by a deputy sheriff. Including each man's campaign and outside spending, their race has cost $13 million, according to the Sunlight Foundation, a bipartisan group that follows campaign spending.
A contest in northeast Ohio pitting GOP Rep. Jim Renacci against Democrat Betty Sutton has drawn $9.7 million in outside spending by the Congressional Leadership Fund controlled by House GOP leaders, House Democrats' campaign organ and numerous other groups.
The only House race where there has been more outside spending is the Pennsylvania contest between Democratic Rep. Mark Critz and GOP attorney Keith Rothfus, where it has surpassed $9.9 million.
(Copyright 2012 by The Associated Press. All Rights Reserved.)